Multiattack. The abomination makes three attacks: one with its claw, one with its bite and one with its sting.

Claw. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (1d8 + 2) bludgeoning damage, and the target is grappled unless it succeeds on a dexterity saving throw.  (escape DC 12).

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (1d8 + 2) piercing damage.

Sting. Melee Weapon Attack: +4 to hit, reach 5 ft., one creature. Hit: 6 (1d8 + 2) piercing damage, and the target must make a DC 12 Constitution saving throw, taking 12 (2d10) poison damage on a failed save, or half as much damage on a successful one.

The Abomination makes a claw attack on an attack of opportunity.