Ceremorphous (5e Template)
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Illithid reproduce via a process known as ceremorposis, which consists of producing "tadpoles" via parthenogenesis, then allowing them to consume the brains of other creatures, eventually mutating them into new Illithids.
Saving Throws. Intelligence
Senses darkvision 120 ft.
Languages Deep Speech, Undercommon, telepathy 120 ft.
Alignment Lawful Evil
Magic Resistance. The Ceremorphus has advantage on saving throws against spells and other magical effects.
Innate Spellcasting (Psionics). The Ceremorphous's innate spellcasting ability is Intelligence (spell save DC save of creature). It can innately cast the following spells, requiring no components:
Tentacles. Melee Weapon Attack: (Str+Prof) to hit, reach 5 ft., one creature. Hit: 15 (2d10 + 4) psychic damage. If the target is Medium or smaller, it is grappled (Creature's Str + 8 + Proficiency Bonus) and must succeed on a DC (Spellcasting DC) Intelligence saving throw or be stunned until this grapple ends.
Extract Brain. Melee Weapon Attack: (Str+Prof) to hit, reach 5 ft., one incapacitated humanoid grappled by the mind flayer. Hit: The target takes 55 (10d10 + Str) piercing damage. If this damage reduces the target to 0 hit points, the mind flayer kills the target by extracting and devouring its brain.
Mind Blast (Recharge 5-6). The Ceremorphus magically emits psychic energy in a 60-foot cone. Each creature in that area must succeed on a DC (Spellcasting DC) Intelligence saving throw or take 22 (4d8 + 4) psychic damage and be stunned for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.