Aeorian Elder Nullifier

Horrid Gnashing. 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:

1–4: The creature is stunned until the end of the turn.

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.

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.

Innate Spellcasting. The nullifier’s innate spellcasting ability is Charisma (spell save DC 24). It can innately cast the following spells, requiring no material components:

At will: counterspell (see “Reactions” below), detect magic, dispel magic, see invisibility

1/day: antimagic field

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

Superior Reaction. The nullifier has 2 reactions each round of combat.

 Mage Bane. The nullifier begins combat concentrating on a 20ft Antimagic Field.

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

Bites. Melee Weapon Attack: +17 to hit, reach 5 ft., one creature. Hit: 22 (2d12 + 10 piercing damage plus 24 (4d12) force damage.

Tentacle. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hit: 16 (1d12 + 10) bludgeoning damage  plus 24 (4d12) force damage. If the target is a creature, it must succeed on a DC 23 Constitution saving throw or its hit point maximum is reduced by an amount equal to the force damage taken. This reduction lasts until the target finishes a long rest. The target dies if its hit point maximum is reduced to 0.

Counterspell. The nullifier attempts to interrupt a creature that it can see within 60 feet in the process of casting a spell.

Spell Vitalization. Immediately after a creature casts a spell of 1st level or higher within 120 feet of the nullifier, the nullifier can move up to twice its speed without provoking opportunity attacks. It can then make one claw attack against a target of its choice.

Parry and Counter. The nullifier adds 5 to her AC against one melee or ranged weapon attack that would hit her. To do so, it must be able to sense the attacker with its vision. If the attack misses, the nullifier can make one tentacle attack against the attacker if it is within reach.