| The Unbreakable Will of the Netherbrain | |||||||||||||
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| Huge Aberration | |||||||||||||
| Level 20 Elder Brain | |||||||||||||
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| Stats | |||||||||||||
| Armour Class | 15 | ||||||||||||
| Hit points |
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| Movement speed | 0 m (0 ft) | ||||||||||||
| Weight | 10000 kg (20000 lb) | ||||||||||||
| Initiative | -15 | ||||||||||||
| Ability scores | |||||||||||||
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| Proficiency bonus | +4 | ||||||||||||
| Saving throws |
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| Conditions | |||||||||||||
 | Will break free of its domination within 5 turns | ||||||||||||
 | Begins with a portion of its HP missing, depending on an earlier ability check | ||||||||||||
 Honour | Gains immunity to recent forms of damage | ||||||||||||
| Features | |||||||||||||
 | Use a reaction to release a brainquake | ||||||||||||
| Actions | |||||||||||||
 | 10d6 Psychic and  in response to damage. | ||||||||||||
 | Mark platforms for negation, destroying them the next turn. | ||||||||||||
| Overview | Combat |
This page focuses on The Netherbrain's behavior during turn-based combat gameplay.
Spells and abilities
Conditions
- - After using Karsus' Compulsion on the Netherbrain
- - If a natural 20 was rolled on the final check to dominate the Netherbrain at the Morphic Pool it will have this condition, which will greatly reduce its HP.
- - On Honour mode only, the Netherbrain becomes immune to all types of damage that was dealt to it the previous round.
Allies
The encounters with Ketheric may involve the following allies for either side. Detailed information in their respective pages.
Enemy allies
Player allies
Encounter
Atop the brain
- Dimension Door, Arcane Gate and Misty Step are all useful spells to have assigned or distributed as scrolls for moving from the entrance to "Atop the Netherbrain", over to the Crown of Karsus.
- Stepping anywhere on the brainy surface will summon tentacles, so it may be easier to approach from the two platforms on either side. Otherwise, if intending to sprint across, using a character who can avoid Opportunity Attacks, such as one with the Mobile feat.
- Globe of Invulnerability is also useful for protecting the caster of Karsus' Compulsion. However, the nearby Mind Flayers will still be able to
creatures inside the globe, which ends the spell prematurely.
- Tossing Mind Flayers over the edge with moves like Telekinesis will not kill them, as they will just reappear atop the Netherbrain.
- Only party members can enter the Netherbrain's Psyche (or The Unbreakable Will of the Netherbrain), so once the portal is open it is no longer necessary to continue fighting other enemies.
Inside the crown
- On Tactician, the Netherbrain will have 450 hit points.
- The Netherbrain's hit point total can be reduced by 20% for the final fight by rolling a natural 20 for the final skill check in the Morphic Pool.
- For each round, the first attack against the Brain will cause it to use Retributive Brainquake, which will damage and potentially Slow everything in range.
- The Brain will use Orb of Negation to summon several orbs which cause damage at the end of the next round. These orbs will destroy the platforms beneath them, so it is important to move characters off of any marked platforms. Further, the brain should be quickly killed before all platforms are destroyed.
- It is strongly recommend to have one's entire party near the portal before casting Karsus' Compulsion. Once the final fight against the Unbreakable Will begins, it is possible for the Netherbrain to negate all platforms near the portal, preventing party members caught outside from entering.
Achievements
Hero of the Forgotten Realms
Save the day: kill the Netherbrain and destroy the Absolute tadpoles.
Absolute Power Corrupts
Reign with terror: take control of the Netherbrain and bend the world to your will.
Sins of the Father
Claim your Throne of Blood: take control of the Netherbrain for Bhaal and break the world.