Stench of the Slug. Any creature that starts its turn within 10 feet of the avatar must succeed on a DC 19 Constitution saving throw or have the poisoned condition until the start of their next turn. On a successful saving throw, the creature is immune to this stench for 1 hour.

Multiattack. The avatar makes four Sickening Claw attacks. It can replace one of the attacks with Insect Gorge (if available).

Sickening Claw. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit:9 (1d8 + 5) slashing damage plus 13 (3d8) acid damage. The target's hit point maximum is reduced by the acid damage taken. The reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0.

Insect Gorge (Recharge 4–6). The avatar disgorges a swarm of biting flies at a point it can see within 300 feet of itself. Each creature within a 20-foot-radius sphere centered on that point must make a DC 19 Constitution saving throw. A creature takes 55 (10d10) piercing damage on a failed save, or half as much damage on a successful one. The biting flies persist for 1 minute or until the avatar is slain. A creature must also make this saving throw when it enters the insects' area for the first time on a turn or ends its turn there.

Caustic Slimepool (1/Day). The avatar causes caustic slime to emanate from itself, covering a 15-foot-radius circle. Each creature within the slime must succeed on a DC 19 Dexterity saving throw or have the grappled condition (escape DC 17). A grappled creature takes 21 (6d6) acid damage at the start of its turn.