Chishinix

If Chishinix fails a saving throw, it can choose to succeed instead.

Chishinix has advantage on saving throws against spells and other magical effects.

Chishinix is always accompanied by a Severed Head.

Chishinix makes two Tentacle attacks.

Melee Weapon Attack +9 to hit, reach 5 ft., one creature. 21 (3d10 + 5) Psychic damage. If the target is Medium or smaller, it has the Grappled condition (escape DC 17) and must succeed on a DC 17 Intelligence saving throw or have the Incapacitated condition until the grapple ends.

Melee Weapon Attack +9 to hit, reach 5 ft., one Incapacitated Humanoid Grappled by Chishinix. 55 (10d10) Piercing damage. If this damage reduces the target to 0 hit points, Chishinix kills it by extracting and devouring its brain.

Chishinix opens a rift into the Far Realm, centered on a point Chishinix can see within 60 feet of itself, and a tentacle lashes across creatures near the rift. Each creature other than mind flayers within 30 feet of the rift must make a DC 17 Intelligence saving throw, after which the tentacle disappears and the rift closes. On a failed save, a creature takes 18 (4d8) Cold damage from the rift plus 18 (4d8) Psychic damage from the tentacle and has the Stunned condition for 1 minute. On a successful save, a creature takes half as much damage only. A Stunned creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

When hit by an attack roll, Chishinix gains a +4 bonus to its AC against that attack roll, potentially causing it to miss. Then Chishinix, along with any equipment it is wearing or carrying, magically teleports up to 60 feet to an unoccupied space it can see.