Multiattack

The tophet makes two Slam attacks. It can replace one Slam attack with a use of Burning Belly.

Slam

Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 16 (2d10 + 5) bludgeoning damage plus 7 (2d6) fire damage, and the target is grappled (escape DC 16) if it is a Large or smaller creature.

Burning Belly

The tophet makes one Slam attack against a target it is grappling as it shoves the creature into its open, flame-filled belly. If the attack hits, the target is forced into the tophet's burning belly, and the grapple ends. While inside the belly, the target is restrained, has three-quarters cover against attacks and other effects outside the belly, and it takes 14 (4d6) fire damage at the start of each of its turns. A creature, including the target, can take its action to pull the target free from the belly by succeeding on a DC 16 Strength check. The creature making the attempt takes 7 (2d6) fire damage.

Gout of Flame (Recharge 5-6)

Flames erupt on a point the tophet can see within 100 feet of it. Each creature within 10 feet of that point must make a DC 16 Dexterity saving throw, taking 35 (10d6) fire damage on a failed save, or half as much damage on a successful one.