An detailed walkthrough of "go there, do this" would ruin the fun, as would a list of secrets that can be found. This page aims at listing the highlights of each area in terms of "what could ruin a hardcore playthrough".

This is also assuming ~Core difficulty, just as a baseline of what might constitute a threat.If playing without "increased enemy" difficulty toggle, some fights may not match the description.

Prologue

Kenabres

Do ask for the crossbow. If we’re going down we’re going down in style. Seriously though, this is actually important for obscure reasons.

Underground

Before the dungeon itself, there’s a chance you might get Demonic Plague from a hit (from a lizard, typically). No starting character can meet the DC to get over it, this is rip.

Dungeon

The big fight is the Water Elemental. Completely optional, even to Sadistict Game Design requirements. No builds and no amounts of buffing will make this fight safe in turn-based.

There’s a room not far from the elemental with 2 groups of 2 mongrels close by. They can be pulled 2 by 2 for a fairly safe fight, but all at once is a Bad Idea.

There’s another room not far from that (in the south-east section) with 4 mongrels to fight at once (a marauder, a ranger, a fighter, and a weakling). This unassuming group might be the hardest fight of the prologue.

Garrison

You cannot handle all the enemies on your own. Let the resistance take care of as much as possible.

That locked door is just bait, you probably can't open and there's nothing noteworthy even if you could.

The boss is a scripted fight designed to be lost. Might as well let it happen, although in Core+ it's unlikely to make any difference.

Act 1

Time-sensitive bit

After a few days, a massive attack wave will reach your basecamp, and you’ll be expected to defend. You’ll want to have as much done as you can before then to make it easier. If you’re fast enough, this can be skipped entirely, resulting in many nameless redshirts saved, and bonus xp/items as a reward.

There are a few enemies that only appear after this attack, most of which are a Bad Idea for hardcore playthrough.

Overall Act 1 is best handled speedily, although a handful of rests will likely be needed.

Mercenaries recruiting

9k XP mark

If you turned on "only active companions receive XP" option at the start of the game, and did not level up your main character during the prologue, he should be level 1 with close to 9k xp.

Exiting the area leaving all companions behind, then re-entering will make you a party of one. You can then grab every last bit of xp available here (free Woljif, etc) and hit the 9k xp mark JUST barely.

The benefit of doing so without leveling your MC is that recruitment prices are based on the level of the MC, but recruits start with your MC's xp.

Hiring

Whether using the above trick to get mercenaries for 500$ a piece, or paying full price, this just might be your last realistic opportunity to buy mercenaries until lategame, as the prices will skyrocket shortly, and much wanted gear has to be paid for.

First day

Before you rest

Complete Woljif's quest. It's easy, straightforward, and out of the way of anything else. Grab Finnean and use it to fill in for weapon types you're missing. Pass him around as needed.

Head to the marketplace and clear the south-east area, recruiting Ember. Build the bridge then proceed west.

This trips many players : having the bridge built is the requirement to accessing other areas. You don't need to clear the entire marketplace right now.

Azatas: you can't afford to hurt Ramien. Side with him, or negotiate for peace.

Aeons: Pickup the purple knife in the square (where the game started).

Avoid for now

SW plaza (vermleks with unavoidable AoE damage) and its burning house. Come back when you have readily available heals & at least resist, ideally protection vs fire spell (scroll).
East: necromancer (you'll need Resist Fear and some AoE crowd control such as Grease)
East: south of the necromancer. The shadows' STR drain on hit require a reliable tank (or expandable pets/summons) , and they should be taken down with magical weapons you lack.

Tower of Estrod

If you never succombed to demonic rage, you'll get a significant buff when entering, instead of a fight.

The skill checks to sneak attack are significant, and failure might lead to a wipe (boss likes to lob Fireballs). Success means ability to push the pillars and get rid of most of the opposition instantly (more so if you're able to bait them in first).

Daeran’s Party

Quite easy area if you're sporting mostly martial classes, especially if you have someone that can Slumber the Schir. He's mini-boss level of danger, but the rest of the opposition is tame.

Azatas: don't miss the singer, she's one of the 3 you're looking for, and will point you to the last. Once you have them all, meet in the church to unlock the Azata path (although you'll only get to make the choice much later).

Wrapping up

Depending on your shape, you may be able to handle some more areas : Silken Thread atelier (although it’d be best to do it on the way back from the Tower) and Pitexian Wine Cellar (north-east). Be careful in the cellar : one of the enemies looks like the others, but wields a magical weapon and hits like a truck. Don't wait until things take a bad turn to give him your best shot. If you’re carrying Camelia around, head straight to Gwerm’s mansion from Daeran’s Estate instead. The last room (hidden babaus) can be a significant threat, as well as the one just before (cambions). As with much of act 1, a good tank will be your best asset. When you run out of steam, head for the Library instead of going back to rest (the dialogue there will teleport you home and save you a trip). The best outcome by far is using the Trickster dialogue path, saving a few lifes and avoiding two fights in the process.

Trickster: You need to pass enough skill checWith Storyteller safe and sound, you can finally rest in relative peace. If this is your first long rest, congratulations, the worst of act 1 is probably behind you.ks to enable the dialogue option, then chose the dialogue option, or you'll be locked out of Trickster path.

Day 2 : finishing up

Market Place

You can clear everything. Just don't take the Brimorak without fire protection, or the shadows without magical weapons. Both are optional. The brimorak fight will yield a broken belt buckle. Make sure you get Storyteller to fix it for you before triggering the Gray Garrison fight, the relic will be invaluable and you won't get another chance until much much later.

There’s also a house with an on-going ritual that you can crush or complete. Completing it summon a Vrock that you’ll have to fight outside (in the north-east corner). This is a difficult fight that brings nothing but XP and bragging rights.

Small areas

Pitexian wine cellar : face ghouls for a couple of magical items. Easy with a good tank, but a single hit might kill a character.
Silken Thread : couple humans including a miniboss. Nothing noteworthy
Topaz solution : maximum danger level. The alchemist lobs multiple nasty explosive per round. Disable him quickly.
Irabeth residence : you'll die without a bit of metagaming (or picking up on subtle clues outside). Short version a succubus will try to mind control your best character. Pre-buff using Protection vs Evil to avoid this. The succubus is then extremely tanky (15+ rounds of fighting is common) but still a very manageable fight, providing you have a tank that can go the distance. As for the heavily armored guard, just disable them (aim their low DEX/WIS saves).

Tavern defense ?

If you're too slow, or if you chose to wait for it, this sequence will play. Level 4 characters shouldn't have much trouble and level 5 none at all. Rely on long-term CC (grease, perhaps web) on the spawn point and the stairs, with ranged attacks to take out most everything.

The fight will take a good long while (1h30 isn’t unusual for a first playthrough), but all that matters is killinig the alchemists when they spawn. Adds are otherwise infinite(?)

Don't let the cow distract you.

If you went through with the sequence, you can find a Nabasu in the Marketplace. This optional and secret fight is absolutely not recommended for hardcore, but hey you're playing hardcore for a reason, right ?

Gray Garrison

First floor

This is your first big "dungeon". Come rested, or rest first thing.

After a few steps in, assuming you gathered allies earlier, you'll receive 1h30 Haste group-wide buff, which is a massive incentive to not rest from here on out (or you’ll lose it).

The most annoying part might be the room filled with Stinky Cloud casting dretches. If you know the one, I’d suggest you avoid it, the XP isn’t worth the aggravation. If you just stumble into it, just drag yourself out as best you can, they'll run out of casts eventually.

There’s a trapper corridor with two small rooms, one of which contains an Azata-summoning tankard. Don’t miss it.The corridor itself will be untrapped by your thiefling friends (if you found them) or require extreme caution.

There’s a secret door leading to the next floor here, but it puts you in a terrible position “stuck in a dead end looking at brimoraks”. If you want to do this, at least Protect and Resist fire beforehand.

Second floor

The council room (upstairs, first door to the left) is a long table that goes into fog of war, with enemies on both sides. Counter-intuitively, you want most of your team to run in to get to the boss (at the end of the table). She’s a summoner, and needs to be dispatched before her summons kick in. If you didn’t side with Ramien, friendly inquisitors will grab aggro from most everything.

The library will solve itself if you picked Trickster choices earlier. Do not forget to grab the storyteller’s notes in the adjacent room.

When you get to the monolith, turn the music up, then pick whatever decision you like most, and laugh like a maniac as you let loose. Even so, be respectful, Minagho has a dreadfully potent spell that might send all your characters to sleep (then death).

Mythic level 1

Some of the choices here are so good that they need to be mentioned

Almost every spellcaster should pick Abundant Casting
Cleaving Shot will be the MVP for much of what comes next
Last Stand negates most bad-RNG spikes. A few lategame encounters cannot, arguably, be won without it (in hardcore).
Personal favorite is Beneficial Curse : Powerless Prophecy for the tanks, if applicable, again to negate many bad-RNG situations (losing initiative rolls)

Act 2

Keep your min/level buffs active at all times from now on.

Keep Haste active at all times (hoard Extend rods)

The additional attack is between 50% and 100% more attacks
The additional speed lets you close in on distant enemies without turning into a porcupine
Helps ensure that 7-10 minutes of buff is enough for every area

Sosiel’s quest (medium-hard)

Rather annoying. You start surrounded, which is never enjoyable, but the fight should be easy. This is one of the very few quest one might consider delaying or outright skipping for a hardcore high difficulty playthrough.

Second big fight is against many melees, some light CC (grease or glitterdust) and average positioning will win this.

Third big fight is one you will lose on Core+. Even if you don’t lose outright, the archers will most likely kill a few of your characters, which you won’t recover from. Go right instead (along the cemetery) and go up the ladder.

Fourth / last fight is obnoxious because the dumbass essential NPC runs in, puts your entire team in an atrocious position (engaged in melee yet surrounded by distant archers). He also can’t die without causing a game over. Proper tanking isn’t possible in that engagement, nor can CC be properly applied as enemies are spread around you, so embrace the only option you have : go berserk and kill them before they kill you.

If you have access to Dimension Door, on the other hand, just mass teleport to the front door (by the two archers) then it becomes a rather normal fight.

Seelah’s quest (medium)

Should be fine as long as you don’t underestimate the babaus. This is the only fight of the zone, so if you’re struggling just go ham.

Moondance Meadows (easy if respected)

Treat this as a major bossfight on Core+. They’re fairly squishy but can deal huge amounts of damage before you get a chance to act, up to and including deleting one of your characters. Send pets ahead if at all possible.

Hellknights rescue (hard)

Outside should be easy. Inside fight may be the worst fight of Act 2 in Core+ if not handled properly (ie with meta knowledge of how the encounter plays out).

The position you start in looks okayish but is actually terrible. The first order of business is getting out of there, NOW. You can’t afford to have everyone waste a round to do that, so have a Dimension Door prepared. You want to be roughly where Regill was during the dialogue.

To some extent this will feel like a DPS check. A lot of Gargoyles will join in, in waves. They will spawn either at the entrance (“waves” 1 and 3) or by where you stand (2 and 4). Some will be casters, all will be immune to your go-to Grease. Glitterdust will help if you’re able to get the entire pack when it spawns, but the key here is to kill them fast enough that you’re never too badly outnumbered.

This encounter alone justifies buying Wide Sweep scythe at camp before hand in spite of the huge (30k) cost.

Leper’s Smile (easy)

Surface level

If you care about saving your troops instead of the loot (neither option has much meaning beyond RP), head up-right then up (look for a crevice and cross it)

The real killer is Gibber, essentially a confusion aura around most enemies. If you know about it though, it's nothing to be worried about. Send in a lone sacrifice and pelt enemies with arrows. The lone hero probably won't suffer much, as enemies have low damage and he won't have anyone but enemies near him to accidentally attack.

The queen is just an extra-strength bag of Gibber, so the same principle apply.

Grotto

Mythic paths requirements
- There's an isolated, beach-like area on the western end, accessible from the start
- Lich: Stash the wand (mandatory). Somehow a thin layer of cloth voids necromantic powers. Go figure.
- Dragon: There an inspectable whatever near the Lich's wand that lets you find Terendelev’s McGuffin, needed to unlock the Dragon path much, much later
Rest of the grotto is optional and mostly yields okay-ish XP and some loot. Fairly safe for regular hardcore, but likely to require a rest or even two to complete.
Swarm ambush
- More Gibber fun, however this time they'll occasionally spawn surrounding you. Very rippy, and cause for skipping this part of the clean-up.
Vrocks
- The threat isn’t dying but attrition, spores do AoE damage and eventually those add up. If you have oracle dips, you’ll be swimming in unused level 1 spells : use those slots for Bless.
- They love casting Mirror Image. Consider direct kills (Slumber, Phantasmal Killer, …) rather than physical attacks.
- Good practice for the rest of the game, as Vrocks are common.
Deraknis
- Looks much worse than it actually is. Easy to hit, shouldn’t last long enough to be a problem
- Does have AoE stuns and confusion, but they love casting it when the fight breaks = so far that they just don’t hit anything with it.
Retriever (giant spider thingy)
- In spite of the looks, it actually feels like a glass canon. Dismantle it quickly in any way you like, but keep a pet on the frontline in case someone has to die.

Before lost Chapel !

After completing Leper's Smile, but before triggering the next camp area, go in Nurah's tent to hopefully spot a vial, and question her about it. This will open up options later.

Heaven’s Edge (pure story)

If you’re super-nice with Daeran, he’ll give you some very powerful wands at the start of Act 3.

Lost Chapel (very easy)

Camp cleanup

When your leave your tent during the attack, go immediately up (to the right of your character, to the left of your screen). Nurah will be there and easy to miss. If you can make the Perception check during this dialogue, you'll open up options later.

Camp cleanup is trivial with mercenaries, as they will be there, unlike companions.

The climb

Make the climb. Not much to it. The church entrance will be a sudden difficulty spike, pay attention and deal with the archers before they can put holes in your backline.

If you’ve kept the Queen around, she’ll pretty much clear the church for you. Otherwise lob a few Controlled Fireballs in there.

Your min/levels buffs should be halfway done, and your team in nearly flawless condition. Now you have a choice : either go right through the illusionary wall (lich den, requires the Wand from Leper’s Smile for peaceful ending) or left (main story boss).

Lost Chapel (Lich secret den)

Lich: Going in here & giving the wand back is the condition to unlock the Lich Path.

Anyone can agree to give up the wand, optionally providing you with reinforcements for the upcoming boss fight and otherwise having no nasty no in-game consequence whatsoever.

Otherwise you might have a seriously rippy fight ahead of you.

The back room on the left has some pretty good loot defended by a few ghosts. The golem is mostly decorative.

Duality of Conjuration and Summoning can be found there and should be used, out of combat if necessary, to get to the scroll granting a permanent +1 Smite Evil cast per day. Resourceful Rage shouldn’t be useful as Rage-based characters will be using Limitless Rage.

Lost Chapel (continued)

You’ll have the option to go down the other side of the hill. Don’t do that just yet. Stay relatively inside until you reach the boss. He’ll open with a strong Hold Person (mass) which can very much ruin an under-prepared group. High saves, Freedom of movement, or extensive baiting of the spell will be required.

The fight will end when Nulkineth dies, the ghouls can largely be ignored.

After the fight, go down the other side of the hill. There are a few paths leading there, it doesn't matter. The gargoyle chieftain is bordering on more dangerous than Nulkineth, and so is Maugla. Exercize extreme caution around those. Everything else is trash-fights (succubus, ghouls, gargoyles). A lot of them.

What you’re looking for is Small Harp and Small sextant bearing the symbol of Desna (a butterfly). Putting them on the matching Shrine will let you play the song of Elysium, and recruit Arueshalae soon.

Ruins of Ashberry Hamlet (extreme threat)

Pretty sure this is only discoverable after finishing Lost Chapel, which is completely stupid since you have no incentive to go over there then. It’s between Drezen and Shallow Grave.

Expect to fight 3 draining ghosts + a boss, at once.

Best : pepper your team with Death Wards
Second-best : hope you didn’t get too attached to those animal companions

Even with mass Death Ward, the boss is a strong spellcaster (Cleric 16 on Core), able to wipe most of your team in a single round. Some of his spells, which he'll use very liberally :

Stormbolts : AoE blast with massive (16d8 = about 70) damage and a stun to top it off.
Rift of Ruin : a Pit-like spell dealing per-round damage to anyone stuck in it, with a DC 35 to escape. Creatures trapped in the Rift are considered “in combat”, so even killing the caster won’t let you close the Rift.

There’s only mediocre XP and a barely magical sword to be found, the only reason anyone would want to clear this now is the requirement for Sadistic Game Design achievement, or the challenge itself.

Drezen (very easy)

Outer grounds

Choice of entrance

Regill: by far the best choice tactically, gets you where you want to be the fastest. But it also locks Regill in your party.
Nurah: trap (duh), but actually quite beneficial as it starts you right next to Arueshalae. Not available if you know Nurah is a traitor.
Default : worst option. A peek into Galfrey's strategical genius.

Easiest way through is finding 3 keys worn by dretches, and using them to secret-ninja-backdoor the last gates instead of bashing Galfrey's thick head against them until something gives.

In the prison, in front of Arue's cell

In the Tavern (due East)

In the Chapel (due West)

No matter how you go about it, you'll end up meeting Mr Giant Demon, who'll open the fight by thoroughly debuffing you. Welcome to the danger zone.

Re-apply fire protection and haste as soon as possible
Move everyone far, far away (dimension door if you have to)
Don't engage. This is a scripted fight. The boss will throw Massive (but caster-centered) AoE spells during 3 rounds of absolutely-cannot-be-killed abject game design. Eventually Greybor will run in, do nothing of use whatsover, pretend he's cool, and the fight will just end.

Inner grounds

Rest, enter the dungeon. Free Yaniel (important for secret end only). The athletics check next to her is very hard, only gets you a (good) weapon you probably won’t use, and costs you a few hours if you fail the check.

The 3 stone tablets in a small room let you disable the zone-thing, but every skill check failure will summon 1-3 ghosts. Good time to use short-term buffs.

Before you go down the stairs to the right, Protect from Evil as you’ll be facing a bunch of mind-controllers.

Get Radiance upgrade from Jorah before you slap some sense into him. Be careful this unequips Radiance, you may be empty-handed when the fight starts. He’s tanky but not a threat. Go for his weak Reflex save if you want to speed things up.

Stairs down lead to an optional bossfight. Let the cultists sacrifice themselves if you want to do it.

This gets real rippy real fast in hardcore. The fully powered boss essentially AoEs on melee hit, so a single tank is much preferable to surrounding him.

If you can crack the lock midway through the large room, you may want to do that. The DC is very high and you lose out on minor XP, but you’d be dodging a very nasty area.

Ghoul pit

The entire encounter is quite clever, in the sense that it can be thoroughly overwhelming if improperly handled, or trivial if well-handled. The easy way through is to back out from the pit as soon as ghouls start spawning. Just use the convenient bottle neck of the corridor to have them come to you instead of being target practice.

Ramparts

You may want to make a hard save when you reach the ramparts. This is where you commit to a Mythic Path.

Last floor

Clear everything left. Bossfight only requires you to kill either of them. The dwarf’s armor inflicts STR damage when he’s hit in close range. He also packs a huge wallop, and summons demons whenever he gets a kill. Minagho is quite likely an easier target.

Hardcore players should note that this fight will likely go either really well, or start getting out of hand and immediatly escalate out of control, with little in-between. In other words, don't be saving for a rainy day.

Act 3

There’s a LOT to do, and all of it can be done in any order. Ivory Sanctum is not a point of no-return, so don’t worry about that.

I’ll try to list the areas by order of difficulty, to give you a vague sense of where to go when.

Getting Woljif back

If you want Woljif back, head for Greengates, he'll meet you along the way. This is the only way to get him back, so if you don't know you might have to do most of act 3 without him.

Getting rid of the dragon

As Irabeth (or whoever) informs you when act 3 starts, there’s a dragon roaming around. She loves to attack you in random encounters if you venture west/north-west.

This can be a death sentence, and should be considered an extreme threat on Core+. Your group will spawn bunched up and in fire breathing range. You can surely see how this could end.

She’ll leave on round 3, or if she gets damaged enough, so you don’t have to fight, but you do need to live. Scatter around, teleport away, protection vs fire if you can (resist won’t help much on Core+, expect breaths of about 100 damage).

You’ll have to choose between dealing with her quickly (somewhat low level) or remaining exposed to such attacks when you travel near her hunting grounds. It’s a bit of a tough call, and entirely up to you.

If/when you decide to get rid of her, fetch Greybor from the tavern, throw him a few gold coins, then go ambush her west north-west from Drezen. You need Greybor to enter.

You’ll then need to track her down to just south of Drezen, and fight her once again, this time to the death. You will be able to buff before engaging.

If Greybor dies in either area, this is game over. When the dialogue ends, Greybor will rush in alone to toothpick the dragon to death.

You cannot shame him to death (yet) without game over, so stack defences and/or consider extreme options such as having someone run to Dimension Door him to safety, etc.

Small and easy areas

All NPC quest-areas unless explicitly stated

Seelah’s might be both the easiest of the most rewarding in terms of XP. It usually kicks in very late in act 3 though.

Arueshalae’s questline, if romancing her, only completes after you get her out of jail. This kicks in so late in act 3 you may need to actively delay the point of no-return.

Ashen Grotto

The swarms require nuking (complete immunity to weapons), don’t come here without at least a few fireballs (or similar) ready, ideally from 2+ characters.
The ogres have “splash damage”, and the boss in particular has countless attacks of opportunity. If you try to use weak summons that like to move around (Animate Dead for instance), they will trigger him and anyone around wil die.

Shrine of sacrilege

Very easy. Hold on to the “Blitz Cut” weapon, the DR bypass will help with a few regenerating enemies later.

Molten scar

Just a few average Vrocks.

The paper may be important later (for secret ending), but you’ll need to give the right answers to Storyteller to make use of it, so pay attention to what’s happening in this area.

Greengates (easy)

Repair and ring the Bell before proc’ing the bossfight.

Sacred Lands (story)

Pretty much just a large puzzle. Some people hate it. Very optional. Most characters can't solo the last boss, but the doors open when she pops, so bring in the party.

Wintersun (very hard)

Most of the area is barely medium+, but it contains several very hard encounters.

Looting the sarcophagus thingy causes ghosts to appear and attack you in several places in the area. They’re strong enough on their own, but if you haven’t cleared the area you’ll have to deal with them AND the regular population at once. This will get ugly. Your best option is to avoid picking the item entirely, or grab it on your way out.

The large pack of marauders/druids/whatever in the bottom left corner needs to be taken very seriously or things will go from fine to catastrophic quickly. They are no threat if you open with suitable spells though (AoE crowd control in particular).

There’s a Treant fighting babaus after a rock bridge. He looks like other Treants but he is massively more powerful. Treat him as a full-blown boss and it should go well, but if you wait until you see the danger it'll be too late.

Last and possibly least, the actual story-related bossfight. He has a lot of attacks (throwing axes) and a pet white dragon. Resist/Protect against frost and have someone offtank the dragon.

Blackwater (very hard)

You need reliable ways to deal electrical damage. Bring shocking weapons, even bad ones, in alt equip slots. Cantrips (jolt) can also be used in a pinch, and the Blitz Cut can finish off the mobs, although this might be a bug.

Enemies will generally have good saves and fantastic AC. One of the last areas you’ll want to tackle in act 3, even though you’re baited there right from the start.

The central roundish platform over the lava should prove particularly challenging.

Boss is actually trivial, just have various characters run to the corner pillars to deactivate the force field, then gently slap the boss. Or teleport to him and gently poke him. Just don't mess around and let adds join in.

Don't leave without grabbing the Stormlord's Resolve. They

convert all your damage to electricity (which isn't great in itself but) lets Ascendant Element : Electricity benefit all your spells
provide most electricity-based spells (chain lightning, stormbolts, ...) to spontaneous casters, who typically lack in spells known.
grant eletricity resist 30 as a minor but welcome benefit

Ivory Sanctum (up to very hard)

Codes can be tricky to understand, and punitive to get wrong.

The right path after the dragon eggs has three gizmos that can be activated to spawn a ghost minotaur each. They are really strong, with many attacks of opportunity (messes with Wolves) and very strong fears. Getting all three then opening a secret door (through a code in the room with many chests) lets you spawn Big Daddy ghost minotaur. He gets healed every round (as per the spell) if you fight him where he spawns, so either use everything you have to burst him down, or kite him a bit.

The large room where they experiment on demons needs to be taken seriously.

The bridge outside should be surprisingly easy because the topology is perfect to have your best tank be the only target.

Xanthir is pretty much the only boss with “phases”.

Phase 1 : regular Xanthir, pretty average fight with weak demons around
Phase 2 : he splits into many swarms.
- Martial characters are utterly worthless for this phase
- On the other hand, some classes are astoundingly talented at handling swarms, like Kineticists.
- If you were ever going to swap in substitutes for that one fight, this is it. The swarms aren't just immune to physical damage, they're also tanky enough to require multiple casts
Phase 3 : nothing to it

Midnight Fane

Aivu’s plan (Azata exclusive, very easy)

Shockingly, a surprise attack is a better plan than sitting on your hands for a month so that the queen can say “I was there”. Another brilliant epiphany regarding her leadership skills.

You’ll piss off Galfrey and she’ll strip you of your title, but she was pretty much always going to do that.

Stupid Galfrey's plan (medium/hard)

Same pathing as the above except the demons will have spent a month gathering forces. This time you may need a rest midway.

Also this time there may be a point to responding to the horn, as you may be able to formally keep your title if you do. This has fairly complex ramifications, but the bottom line if you ask me is that you shouldn’t care unless you respect Galfrey, RP-wise.

Which you won’t by the time this area is over.

Also if you’re concerned about getting a “perfect” ending, getting stripped of your title is the easiest way to save everyone while still unlocking the secret ending, even getting the title back along the way.

Ending

If you’re looking to secure the best ending, including secret ending, give Galfrey the Lexicon if you’re going for a Mythic Path that somewhat aligns with her values (Angel, Azata, etc). This is the easiest way to unlock the secret ending without causing Irabeth to die.

If you’re an Angel, you might as well make a move to retain your title entirely. You’ll still want to give her the Lexicon to minimise casualties (Galfrey herself). Maybe.

Secret Area (rip)

Closing all doors except the two marked ones (open everything at first, then do another loop) opens up stairs in the central room. This leads to a very small area with a huge-DC trapped container. SAVE. Wait you can't this is hardcore... Well, re-think a few choices then, like do you really want to clear this area now ?

Disabling the trap is possible, but will not prevent enemies from spawning when you try to open the container.

The swarms are immune to attacks, are massively resilient to damage anyway (hundreds of HP) and while a tank could survive a few hits, the rest of your party probably can’t. The close quarters stacks the decks heavily in favour of the swarms (AoE hits), especially since they don’t spawn in one single spot.

At the very least, you absolutely want to over-prepare, especially when it comes to party composition and prepared casters spell selection. There are probably exceptions I’m not aware of, but by and large

You won’t be able to apply any CC
- Trips, grease, etc
- Pit-based magic
You won’t be able to use your go-to defensive layers
- AC is meaningless, so is Protective Luck and the likes
- Aggro cannot be managed/exploited
You won’t be able to kill them all before they can act in a fair fight

If you’re not struggling here, you're easier on a difficulty that is much too low, or should be writing guides, not reading them !

If you’re reading this looking for a way out, the cheesiest known method, and possibly the only one that works on the highest difficulty settings, is to fill the area with delayed or on-going damaging effects such as Blade Barrier, bunch up in a corner, and send someone to die triggering the swarms.

Assume you’ll need to rest right-before and right-after and don’t try to save on resources.

Playful Darkness (maybe rip)

This is one of the optional bosses that can very, very easily wipe your group. You’ll find him on the far north of the abyssal plane, in a fairly secluded, bone-filled, cave. DO NOT engage unless you’re ready.

Several adds will spawn in the corridor, but if they’re any threat you don’t stand a chance against the boss himself.

Statistics on Core

718 hit points
AC 58
Flat-footed AC 49
Saves +36/+31/+28
Spell resistance 36
DR 10/Adamantine

He has a lot of attacks per round, and you can safely assume they will be enough to hit any AC (Core+). He’s very much buffed (active spells) when the fight starts, and removing those should be your priority.

Common strategies to deal with him

Keep him busy/distracted with non-companion characters
- Azata (trees) and Herald Caller are particularly good at this. The sheer number of summons can exceed his damage output.
- Undeads are far more resilient to his attacks, so I’m guessing (but didn’t test) that Lich has massive advantages on this front
OR with a super-tank
- You absolutely want Protective Luck if you’re going down that road. Getting hit even 5% of the time is too much for this fight.
(Greater) dispel his buffs IF you have a superb caster available for that
Handle his adds first to secure your backline

Dealing with bosses

Important : this DOES NOT apply below Core difficulty.

Why talk about this now ? Because Playful Darkness was the perfect illustration of how Core+ teams should tackle the strongest enemies.

Normal characters simply will not be able to make any dent into a boss. They fall short by at least 30 Attack Bonus. The same would apply to spellcasters (Spell resistance and high Saving throws).

You can either have the main character be strong enough through the combination of Mythic Path exclusive stuff and companion buffs to single-handedly destroy strong enemies.

OR

You build your entire party so that everyone brings strong, team-wide, stackable buffs.

Most mythic paths come with strong team-wide defensive buffs, but not many bring any offensive benefits and none just outright enable getting carried by companions (that I know of).

Can <your mythic> handle a boss by himself ?

Those are just rough guidelines of baseline power levels especially targeted towards newcomers. There are ways to stack obscure, complex or outright broken mechanics to omg-i-strong level PathsI consider weak, sure, I guess, but this isn’t the right place for that and I honestly don’t care ;-)

On the other hand some people have pointed out that recent updates have brought significant buffs/nerfs that mandated re-evaluations (Aeon), or contributed to areas I lacked experience with and I am very grateful for that ! Unfortunately, the best I can do is point to my own ignorance and recommend you look for better information.

Aeon : No. Got buffed significantly since. Unclear.

Angel : Very much. Offensive spells are massive, unavoidable numbers. Defensive spells bring immunity to most ailments (to everyone, for a single spell slot).
Azata : Very unlikely. Many superpowers increase your numbers (AB, DC), but it probably lacks a little something on top.
Demon : Not really
Devil : No
Gold Dragon : Unlikely even after patches
Legend : Yes for super-optimized builds, but the general population will be nowhere near.
Lich : Yes.
Trickster : Absolutely. Boost your damage / neglect your AB, Trick Fate. Every attack is now a crit. For 3 rounds, then it's nap time.
Swarm-that-walks : Not like they'll get any help.

Act 4

Make sure you loot the Balor boss before entering the Abyss, specifically the weird Coin he has on him. It will be used to teleport to “town” for the entire act.

City’s a bit difficult to navigate until you get a hang of it. Short version is that a given camera angle always leads to the same openings (for instance looking North will always trigger those stairs to appear).

Dimension Door

Many rooftops can be accessed by teleporting and will contain a variety of strong trap, magical items, and optional enemies.

With a few exceptions, these will be optional bosses, as in “stronger than regular bosses”. Particular care should be taken against the Deathsnatcher (massive fear) and the Quasit (kill the adds or they’ll add up across three phases, and those succubi have huge damage per round).

It is strongly recommend to keep a scroll of Mass Dimension Door on you. You won’t be able to rest, and could very easily get stuck and spend the rest of your life on a rooftop if your regular casters get disabled. “But I have resurrection” will not suffice.

Angel mythic path

The mythic questline is really annoying because you might have locked yourself out of the best resolution by the time you get it.

Essentially you want three keys

One requires Yaniel to be there when you kill Minagho
- But you can kill Minagho before Yaniel arrives → key denied
One requires Berenguer to be let loose on the city. This is fine.
One’s related to the Aasimaar slaves
- Memory’s fuzzy on this one
- As I recall you can’t find the keys without the slaves pointing it out
- They won’t point it out without a specific dialogue path
- You may need to have the quest before dealing with them / the owner

Rune-thingy hidden quest

There will be three spots outside where a small hole in walls can be inspected with a difficult Religion check. You’ll then need to procure a rune (over a still-warm dead body, of course) that fits in these walls, in a specific order (you can’t get it wrong).

Each time you’ll get attacked, and the rune will grow stronger.

You can then use it to access a hidden area near Shamira’s for a very tough fight and a significant reward.

Battlebliss Arena

Perfect example of “everyone is an asshole”. Doesn’t matter whom you side with, who dies, etc. They all suck, and you can’t kill them all.

Once this is over, re-equip your actual amulet ← you will forget.

Shamira

Feel free to defy her, but that won’t be easy. You’ll need to pre-buff a lot to succeed.

Whatever you do, do not mention the purple knife. She’ll take it with no way to fight her for it.

Vellexia

Keep her interested by mixing your replies (good, evil, etc) for bonus loot.

Fighting her is tough and entirely optional, but brings good xp, excellent loot, and a deep satisfaction.

Slave Market

Freeing Suture one way or another is required for secret ending purposes. Older game version (1.x) needed to explicitely buy his freedom.

Also you’re probably going to die if you just challenge the leader outright, as everyone will jump in. If you want to purge the swamp, trigger as many secondary demons as possibly before openly declaring war to the leader. Particularly relevant to Azatas.

Leaving the city

Before you leave, explore Nocticula’s palace. The large halls actually have openings on either side, and one of them leads to Areelu’s quarters. Second half of the Lexicon is hidden there, and you need it for the secret ending.

There are clear signs of dropped/unfinished content. You can gather/hire various crews to get out, which leads me to believe that at some point you were meant to go after Hepzemirah without having to meet Nocticula.

I have not found a way to skip the Nocticula audience, and she always lets you proceed ahead without making any demands.

The various crews offer slightly different dialogue paths, but nothing worth writing (or reading) about. Don’t worry if you get jailed.

Big scary dragon

That's actually a good way to think of her. Fear is the main issue, so make sure you're immune somehow. Then it's just a regular high-stats mook.

Goat daddy

VERY rippy encounter, no matter your build, party, etc. Before the fight kicks in you'll be mass-debuffed (the only true fight where this happens). You'll need to decide which buffs you need back up first, because he's not going to wait for you to be ready. Angels have a decent edge here, as a single cast covers most critical buffs.

On top of all the usual nastinesses cranked up to DemonLord level, you should also expect him to Baleful Polymorph one of your characters, typically your best caster, with a duration of {permanent} and a DC of 36 in Core, which is (far) above what your other casters are likely able to Remove Curse.

Popular wisdom is to further Baleful Polymoph the character, overriding the DC with an easier one (bit cheesy), or reconsider if permanent doesn't actually mean "until death", and the relative triviality of bringing someone back.

Snake lord

Very close to Goat Daddy is a small lava-surrounded island, only accessible through teleporting. The mobs there may aggro (to no effect as they can't reach) before you reach there. This is also where you might realise that your go-to Dimension Door caster now has a snout and no hands. See above.

Anyway, teleport there, handle the tough but unremarkable encounter, and loot the +2 tome before heading out of the mines.