Abomination's Ruinous Physique. The Hexjaw regains 10 hit points at the start of its turn. If the Hexjaw takes radiant damage, in regains no hit points at the start of its next turn. The Hexjaw dies only if it is reduced to 0 hit points by radiant damage or takes radiant damage while at 0 hit points.

Abominous Resistance. The Hexjaw has advantage on saving throws against spells and other magical effects.

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit: 17 (2d12+4) piercing damage plus 6 (1d12) necrotic damage and the target cannot regain hit points until the beginning of the Hexjaw's next turn.

Thunderous Screech (Recharge 5-6). The Hexjaw releases a blast of sonic might in a line 10 feet wide and 60 feet long. All creatures within the line must make a DC 15 Constitution saving throw, taking 22 (4d10) thunder damage and being Deafened for 1 minute on a failure or half as much damage and not being Deafened on a success. While Deafened in this way creatures have disadvantage on Dexterity based checks and saving throws, and a creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Mana Hyped (3/Day). As a reaction to succeeding a saving throw against a magical effect, the Hexjaw can roll to regain its Thunderous Screech, move up to half its speed, and take one action.