Remorhaz

Heated Body. A creature that touches the remorhaz or hits it with a melee attack while within 5 feet of it takes 7 (2d6) fire damage.

Monstrosity Resilience. The remorhaz is resistant to exhaustion and to the frightened condition.

Tunneler. The remorhaz can burrow through ice, snow, and permafrost, and it leaves a 5-foot-diameter tunnel in its wake.

Bite. _Melee Weapon Attack:_ +11 to hit, reach 10 ft., one target. _Hit:_ 40 (6d10+7) piercing damage plus 10 (3d6) fire damage. If the target is a Medium or smaller creature, it must succeed on a DC 17 DEX save or be swallowed by the remorhaz. A swallowed creature is blinded and restrained, it has total cover against attacks and other effects outside the remorhaz, and it takes 10 (3d6) acid damage and 10 (3d6) fire damage at the start of each of the remorhaz's turns. If the remorhaz takes 30 damage or more on a single turn from a swallowed creature, the remorhaz must succeed on a DC 19 CON save at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the remorhaz. If the remorhaz dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 15 feet of movement, exiting prone.

Vent Heat (119 HP or Fewer). As the remorhaz's life force ebbs, its body generates more heat to protect itself. It can open valves in its carapace to vent this excess heat. Each creature within 5 feet of the remorhaz must succeed on a DC 17 CON save or suffer one level of exhaustion.