Aeorian Nullifier

The nullifier's mouths gnash incoherently while it can see any enemies. Each creature that starts its turn within 20 feet of the nullifier and can hear it must make a DC 16 Wisdom saving throw. Unless the save succeeds, the creature rolls a d8 to determine what it does during the current turn:
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1-4:
The creature is Stunned until the end of the turn.
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5-6:
The creature is Frightened until the end of the turn and uses its movement to get as far as possible from the nullifier.
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7-8:
The creature doesn't move, and it uses its action to make one melee attack against a random creature (other than itself) if one is within reach. It otherwise does nothing

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

The nullifier makes three attacks: one with its bites and two with its claws.

Melee Weapon Attack +8 to hit, reach 5 ft., one creature. 17 (2d12 + 4) Piercing damage plus 11 (2d10) Force damage.

Melee Weapon Attack +8 to hit, reach 10 ft., one target. 11 (2d6 + 4) Slashing damage plus 11 (2d10) Force damage, and the target is Grappled (escape DC 16) if it's a creature. The nullifier has two claws, each of which can grapple one creature.

The nullifier attempts to interrupt a creature that it can see within 60 feet in the process of casting a spell. If the creature is casting a spell of 3rd level or lower, its spell fails and has no effect. If it is casting a spell of 4th level or higher, the nullifier makes a Charisma check with a DC equal to 10 + the spell's level. On a success, the creature's spell fails and has no effect.