You’ve spent over a hundred hours hoarding elixirs you’ll "save for later" and agonizing over whether to trust a dream visitor who eats brains. Now, you’re finally standing at the base of the High Hall, looking up at a giant brain that wants to rewrite reality. Most people treat this fight like a standard turn-based slog. They try to kill every single enemy on the way to the Crown. Honestly? That’s a one-way ticket to frustration and a potential Honor Mode wipe.
The bg3 final battle guide isn't about being the strongest person in the room. It’s about being the fastest and the most annoying. If you’re playing on Tactician or Honor Mode, the game stops playing fair, and you should too. This fight is a sprint, not a marathon.
The Secret to the High Hall: Stop Fighting Everything
Seriously. Stop it. The courtyard leading to the final climb is a trap designed to drain your level 6 spell slots before the real fight begins. You’ll see your allies—the Harpers, the Hellriders, maybe even a very angry owlbear—charging into a meat grinder.
Basically, you have two choices here. You can spend two hours clearing the courtyard, or you can use Greater Invisibility or Potions of Speed and just... leave. If you reach the doors at the far end, your party teleports to you. You don’t get an achievement for killing every nameless cultist in the city. Save your juice for the brainstem.
Once you’re past the initial gates, you’ll hit the "Point of No Return" healing station. Use it. It’s one of the few places in the final sequence that acts like a Long Rest, restoring every single resource. If you have a Cleric, this is the time to cast Heroes' Feast and Level 6 Aid. These buffs persist, and they are the only reason your wizard won't get one-shot by a stray Magic Missile later.
Atop the Netherbrain: The "Call Ally" Mistake
When you finally climb that brainstem and see the Red Dragon, it’s tempting to start clicking every "Call Ally" button on your hotbar. Don’t. Every time you summon an ally, you’re using an Action. In the first two turns, your Actions are worth more than a group of City Watch archers who are just going to get incinerated by dragon breath.
The Red Dragon has a massive health pool and a nasty reaction called Draconic Retaliation. If you hit it, it hits back. Hard.
- The Strategy: Ignore the dragon. I know, it sounds insane. But unless you have a Paladin who can delete it in one turn with Divine Smite crits, it’s a distraction.
- The Real Targets: Focus the four Illithid Arcanists on the side platforms. These guys will spam Magic Missile and stun your party. If your "concentrating" character gets stunned, your progress on the Crown resets.
- Mobility is King: Use Misty Step, Dimension Door, or the Illithid Fly ability. You need to get your Mind Flayer (whether it’s you, Orpheus, or the Emperor) to the Crown of Karsus immediately.
Opening the Portal (The Most Nerve-Wracking 2 Turns)
Once your Mind Flayer reaches the Crown, they have to use Karsus’ Compulsion. This is a channeled spell. If they take damage or get CC’d, the timer resets.
This is where you use the most broken spell in the game: Globe of Invulnerability.
Drop that shimmering golden dome right over your Mind Flayer. Now they can’t take damage. You can even shove your entire party inside it. While the dragon and the Dream Guardians are wailing on the outside of the bubble, you’re just chilling, waiting for the portal to open. It feels like cheating, and honestly, it kinda is.
Inside the Mind: The DPS Race
The portal opens. You go inside. Now you’re facing the Netherbrain itself. You have roughly 3 to 5 turns (depending on difficulty) before it deletes the platforms you’re standing on and kills you instantly.
One thing people get wrong: they rush in one by one. Do not do this. The brain has a reaction called Retributive Brainquake. It triggers on the first person who attacks it each round. Send in a "tank" or a summon to eat that first reaction, then bring in your heavy hitters—your Rogues, your Sorcerers, your Fighters—to dump their highest damage-per-second (DPS) attacks.
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Pro Tip: The brain becomes immune to the damage types you used in the previous turn. If your Wizard casts Disintegrate on Turn 1, the brain is immune to Force damage on Turn 2. You have to vary your elements. Have Gale swap between Cold, Fire, and Lightning. Have your Fighter switch from a physical bow to elemental arrows like Arrows of Dragon Slaying (which, surprisingly, work very well here too).
Actionable Next Steps for Your Run
To wrap this up, if you're staring at the Morphic Pool right now, here is your checklist:
- Check your scrolls: Ensure every character has at least two Dimension Door scrolls.
- Stock up on Speed: Potions of Speed are better than the Haste spell because they can’t be broken by losing concentration (though you do get "Lethargic" when they wear off, so timing is everything).
- The Globe is Life: If you don’t have a Wizard with Globe of Invulnerability, go find a scroll in Sorcerous Sundries before you leave the city. You will regret not having it.
- Positioning: In the final brain phase, stay spread out. If two people are on the same platform and the brain targets it with an Orb of Negation, you’re losing half your team in one go.
The final battle is less about "winning" a fight and more about surviving a chaotic environment. Keep your eyes on the Crown, keep your Mind Flayer protected, and don't let the dragon bait you into a brawl you don't need to win.