Ash Ghast

Smog. Any creature that starts its turn within 5 feet of the Ash Ghast must succeed on a DC 12 Constitution saving throw or be poisoned until the start of its next turn. On a successful saving throw, the creature is immune to the Ash Ghast's Stench for 24 hours.

Blazing Defiance. The Ash Ghast and any Burning Ghuls within 30 feet of it have advantage on saving throws against effects that turn undead.

Smolder.  A creature grappling or grappled by an Ash Ghast takes 2d6 + 2 fire damage at the start of its turn per Ash Ghast that is grappling/grappled-by it.

Extinguishable. If an Ash Ghast is ever completely submerged in water or buried in sand, dirt, or another material sufficient to completely smother its fire, it loses half its hit points and becomes a Ghast.

Ashen Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one creature. Hit: 13 (2d8 + 4) piercing damage and 9 (2d6+2) fire damage.

Fire-Tainted Claws. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage and 9 (2d6 + 2) fire damage. If the target is a creature other than an undead or a construct, it must succeed on a DC 12 Constitution saving throw against poison or be paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.