Aversion of Decay. If the golem takes necrotic damage, it has disadvantage on attack rolls and ability checks until the end of its next turn.
Immutable Form. The golem is immune to any spell or effect that would alter its form.
Limited Magic Immunity. The golem can't be affected or detected by spells of 4th level or lower unless it wishes to be. It has advantage on saving throws against all other spells and magical effects.
Magic Weapons. The golem's weapons attacks are magical.
Innate Spellcasting. The golem's innate spellcasting ability is Wisdom (spell save DC 15). It can innately cast the following spells, requiring no components:
At will: detect thoughts, telepathic bond
3/day: charm person, major image
1/day: confusion, dominate person, modify memory
Multiattack. The golem makes two slam attacks. Unless it uses Mind Blast
Slam. Melee Attack: +9 to hit, reach 5 ft., one target. Hit: 18 (3d8+5) bludgeoning
Mind Blast (Recharge 5-6). The golem magically emits psychic energy in a 60 foot cone. Each creature in that area must succeed on a DC 15 Intelligence saving throw or take 22 (4d8+4) psychic damage and be stunned for one minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on a success.
Description
A brain golem was an eight-foot-tall humanoid-shaped construct made entirely of brain tissue with a bud of an elder brain for a head. These creations existed only to serve an elder brain and its illithid community. They did not communicate in any way and only reacted to the telepathic orders of mind flayers, and could not attack any mind flayer.
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