Tophet

Fiery Heart. A tophet's inner fire can be ignited or doused at will. Its heat is such that all creatures have resistance to cold damage while within 30 feet of the tophet.

Burning Belly. Creatures inside a tophet's burning core take 21 (6d6) fire damage at the start of each of the tophet's turns. Escaping from a tophet's belly takes 10 feet of movement and a successful DC 16 Dexterity (Acrobatics) check.

Multiattack. A tophet makes two attacks, no more than one of which can be a gout of flame.

Slam. Melee Weapon Attack. +10 to hit, reach 5 ft., one target. Hit: 12 (1d10+7) bludgeoning damage. The target is also knocked inside the tophet's burning belly if the attack scores a critical hit.

Gout of Flame. The tophet targets a point within 100 feet of itself that it can see. All targets within 10 feet of that point take 22 (4d10) fire damage, or half damage with a successful DC 16 Dexterity saving throw.