Cthulhi

Shapechanger. The cthulhi can use its action to polymorph into a beast form that resembles a rat (speed 20 ft.), a raven (20 ft., fly 60 ft.), or a spider (20 ft., climb 20 ft.), or back into its true form. Its statistics are the same in each form, except for the speed changes noted. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Eldtrich Sight. Magical darkness doesn't impede the cthulhi 's darkvision.

Magic Resistance. The cthulhi has advantage on saving throws against spells and other magical effects.

Surprising Strength. The cthulhi has strength beyond its size, whenever it makes a slam attack a contested strength check must be made. If the opponent fails the fall prone.

Slam. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 5 (1d4 + 3) bludgeoning damage.

Invisibility. The cthulhi magically turns invisible until it attacks or until its concentration ends (as if concentrating on a spell). Any equipment the cthulhi wears or carries is invisible with it.