Huge monstrosity, unaligned

Armor Class: 16

Hit Points: 20d10+80

Speed: 40 ft , burrow: 40 ft , climb: 10 ft

STR

20 +5

DEX

10 +0

CON

18 +4

INT

2 -4

WIS

12 +1

CHA

5 -3

Saving Throws: STR +8, CON +7

Skills: Stealth +3 (while burrowed)

Damage Resistances: Fire, Bludgeoning from nonmagical attacks

Condition Immunities: Prone

Senses: Tremorsense 60 ft., Darkvision 60 ft., Passive Perception 11

Challenge Rating: 7 ( 2,900 XP)

Proficiency Bonus: +3

Actions

Multiattack. Slagmaw makes two Slam attacks.   Slam. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 2d10+5 bludgeoning damage plus 1d8 fire damage.   Lava Spit (Recharge 6). Slagmaw spits a glob of lava at a point within 60 feet. All creatures in a 10-foot radius must make a DC 15 Dexterity saving throw, taking 6d8 fire damage on a failed save or half as much on a success.   Tunnel Crush (1/Day). Slagmaw slams into the ceiling, causing debris and molten rock to fall in a 20 ft. radius. Each creature must succeed on a DC 16 Dexterity save or take 4d10 bludgeoning damage and become restrained until freed (DC 14 STR check).

Legendary Actions

Burrow Shift. Slagmaw burrows up to 20 feet without provoking opportunity attacks.   Heat Pulse. All creatures within 10 ft. take 2d6 fire damage.   Molten Quake (Costs 2 Actions). Slagmaw causes the ground in a 15-foot radius to quake violently. Each creature must succeed on a DC 14 Strength saving throw or be knocked prone.

Lair Actions

On initiative count 20 (losing ties), Slagmaw can take a lair action:   Boiling Ground. A 10-ft. radius area becomes superheated. Creatures that start their turn there take 2d10 fire damage.

Suggested Environments

Underground, Volcanic, Elemental Plane of Fire