Incorporeal Movement. The allip can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object.

Multiattack. The allip can make two Maddening Touch attacks.  It can replace one with a use of Howling Babble if available. 

Maddening Touch. Melee Spell Attack: +7 to hit, reach 5 ft., one target. Hit: 18 (4d6 + 4) psychic damage.

Howling Babble (Recharge 5-6). Each creature within 30 feet of the allip that can hear it must make a DC 16 Wisdom saving throw. On a failed save, a target takes 18 (3d8 + 4) psychic damage, and it is stunned until the end of its next turn. On a successful save, it takes half as much damage and isn’t stunned. Constructs and undead are immune to this effect.

The Allip has 3 legendary actions which it can use at the end of another creatures turn. The Allip gets its legendary actions back at the start of its turn but cannot use each action more than once per turn.

Incorporeal Shunt (1 action). The allip teleports up to its movement speed without provoking opportunity attacks,

Whispers of Madness (2 action). The allip chooses up to three creatures it can see within 60 feet of it. Each target must succeed on a DC 16 Wisdom saving throw, or it takes 13 (2d8 + 4) psychic damage and must use its reaction to make a melee weapon attack against one creature of the allip’s choice that the allip can see. Constructs and undead are immune to this effect.