Bassigator

Amphibious. The Bassigator can breathe air and water.

Leaping Lure. The Bassigator has advantage on attack rolls against any creature that moved on its last turn while within 30 feet of water.

Pack Tactics: The Bassigator has advantage on an attack roll against a creature if at least one of the Bassigator's allies is within 5 ft. of the creature and the ally isn't incapacitated.

Aetheric Mutation. The Bassigator counts as both a beast and fey, and it exudes faint magical energy. Spells that detect or identify fey register its presence.

Incorporeal Movement. The bassigator 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 Bassigator makes two attacks: one with its bite, one with its tail slap.

Bite. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 18 (2d10 + 5) piercing damage. If the target is a Medium or smaller creature, it is grappled (escape DC 16). Until this grapple ends, the Bassigator can't bite another target.

Tail Slap. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 15 (2d8 + 4) bludgeoning damage. If the target is a creature, it must succeed on a DC 15 Strength saving throw or be knocked prone.

Magical Jet Spray (Recharge 5–6).
The Bassigator unleashes a surge of enchanted water in a 30-foot cone. Each creature in the area must make a DC 14 Dexterity saving throw, taking 21 (6d6) force damage on a failed save, or half as much on a successful one. A creature that fails the save is also pushed 15 feet away and knocked prone.

Death Roll. If the bassigator has a creature grappled by its bite, it can use its bonus action to death roll, causing the grappled creature to take 10 (3d6) Bludgeoning bandage. Doing so, however, will make it unable to move or take reactions until the start of its next turn.

Aetherfade (3/day). As a bonus action, the bassigator can choose to make itself invisible for 1 minute or until it attacks, casts a spell, or forces a creature to make a saving throw.

Counterspell (recharge 5-6). The bassigator cast counterspell at third level (using wisdom as its spell casting ability).