The journey through BG3 will eventually lead you against the Netherbrain. The finale sees you and your allies go up against the Illithid and the Absolute, with multiple significant showdowns occurring on your way to reaching the Netherbrain before the final battle.
There are a lot of tactics you need to consider when heading into the final battle with the Netherbrain in BG3.
How to beat the Netherbrain in BG3’s final battle
In order to beat the Netherbrain in Baldur’s Gate 3‘s final battle, prioritize using characters with high damage output. Characters who can dole out multiple attacks per turn, all while dodging the areas where the arena will crumble are very useful as well. You will need to deplete the Netherbrain’s 210 total health within five turns.
You are going to want your illithid party member (or yourself if you’re an illithid) to make it to the Crown of Karsus first to influence the Netherbrain. Defeat the enemies atop the Netherbrain, and fly, warp, or dash your way to the Crown. Then you must activate and channel the spell to open the portal
If you, as an illithid or your party-member illithid take Stun, Polymorph, or Knock Out damage while influencing the Netherbrain, the process will need to be restarted.
Reach the Crown of Karsus
To defeat the Netherbrain, you must reach the Crown of Karsus. Doing so is difficult as several enemies are atop the Netherbrain, and more will spawn. However, not everyone needs to reach the Crown.
To interact with the crown, you must have your Illithid ally alive, either the Emperor or Orpheus. You’ll need to be within eight meters to activate the spell and then channel the spell for two turns.
Thankfully, there’s the opportunity to heal just before the brain stem, which you need to interact with to reach the final battle, so make sure you do so.
We had several attempts at this mission before finally completing it. We found the best tactic to stick your team together, moving them as far as possible in each turn and attacking along the way.
After four turns, a Nautilod spawns above and drops bombs across the area. It is unlikely you make it to the Crown of Karsus before this happens, so avoid the marked areas that will detonate at the end of the Nautilod’s next turn.
While your allies are weak and can be defeated easily, We recommend spawning them purely for distraction and extra damage against enemies. Even a single turn of not having a companion attacked is a huge bonus.
To get close to the Crown of Karsus, utilize abilities that allow you to fly or warp to a location. If you don’t have any with a character and have no enemies to attack, simply using a dash will suffice.
Taking down the Dragon is not required, though it is advisable if you can due to the massive damage output it does.
Aside from the Dragon’s powerful AOE attacks, the Mindflayer enemies are your biggest problem, as they can easily stun you with an attack, forcing you to miss a turn. If too many of these stack up, the fight becomes even more complicated. We used allies and summoned companions to focus on the Mindflayers, which usually resulted in them being targeted and not members of the party.
After you have activated the spell and channeled it for a turn, a portal will open to take you to the final stand-off against the Netherbrain itself.
Enter the Netherbrain’s Psyche
The Netherbrain has no direct attacks but is a deadly foe, as it will highlight areas of the arena that will be destroyed on the next turn, and it must be defeated within five turns.
Move as many allies through the portal as possible to maximize your attacks against the Netherbrain and whittle down its health as much as possible. However, the priority must be avoiding the areas that will fall away as it’s instant death.
You do not need all your allies to be in the portal and the fight outside will continue. If the Netherbrain is defeated in time, the allies outside are still safe and feature in the final cutscene.
Any ally with multiple attacks in a single turn is precious in this fight, or someone with an attack capable of doing high damage. At 210 health, the Netherbrain is sturdy but can be defeated within the timeframe.
