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"Welcome to my mind!"
Monster Manual classification: Unknown
Alignment: Lawful Evil
Boss: Red Named - Quest Boss
Rare: NoCR: ♣? ♦18 ♥? ♠?
Attack: Egowhip (Charisma damage), Tentacle whip (Bludgeoning damage), SpellcastingSpecial Qualities: SR, DR ♦10 ♠15/Byeshk, Mind Thrust
Habitat: In The Flesh
Description: Yaulthoon is an Illithid. Like all Mind Flayers he has some DR that is bypassed with Byeshk damage. Mind flayers speak Undercommon but prefer to communicate telepathically as you'll see in his quest.
Yaulthoon always fights from a distance, often teleporting around his arena and attacking with his various psionic abilities.
Mind Thrust: This attack is a massive AOE that will hit pretty much everyone in the arena. It deals heavy psyonic damage, and energy drain damage. Will save negates, but requires multiple successive saves.
Spellcasting: At will: Hold Monster, Dominate Monster, Psionic Dominate, Lightning Bolt, Meteor Swarm (Save DC 13 + spell level + mind flayers charisma bonus).
Intellect Fortress: In the realm of the mind this creature is fortified against all direct attacks. Once you destroy two Brain Pods, this buff will disapear for a few seconds.
Telepathy (Su): Mind flayers can communicate telepathically with any creature that has a language, within a great distance. (Mostly a flavour thing, but this explains why Yaulthoon and some other mind flayers are able to speak to you through your mind at a great distance.)
After killing all the Taken from the fashion show Yaulthoon will walk out on stage and do a short monologue. Everything will go black and you will transported to Yaulthoon’s mindscape.
First thing you will notice is purple sack like structures, I’ll call them “Pods”. These are the “souls” Yaulthoon has previously assimilated. They are the key to defeating him. Yaulthoon is on the edge of the mindscape with what appears to be a Tensor's Transformation Shield. He is invulnerable when his shield is up.
Yaulthoon orders his minions -the Taken to attack. He will then start casting all kinds of nasty spells. Fight behind the solid pods, keeping them between you and Yaulthoon. After you have taken out the trash stand behind one of the Pods. Yaulthoon will cast energy spheres at you. The sphere will destroy the Pods. A nice benefit is that anyone standing near a bursting Pod will receive a boost to their hitpoints and spellpoints.
On higher difficulty settings you'll need to defeat several additional enemies during the waves of taken as well, particularly deadly are the beholders on elite.. Slay them quickly.
After about three Pods have popped Yaulthoon will become vulnerable. Time to hammer the squid face. Just be careful not to fall off the edge when you run up to him. If you do fall off you will be teleported back to the middle of the mindscape. After a bit his shield will regenerate and the more minions will show up again. Near the end you will start to see 3 fleshy pods near yaulthoon, smash these to interupt his attacks and ensure you can contiue to beat him down. Avoid death at all costs. Yaulthoon is healed whenever a party member dies.