Lava Glide. The elemental can burrow through lava, earth and stone. While doing so, it leaves behind a pool of lava.
Lava Form. The elemental can move through a space as narrow as 1 inch wide without squeezing. A creature that touches the elemental or hits it with a melee attack while within 5 feet of it takes 2d10 fire damage.
Siege Monster. The elemental deals double damage to objects and structures.
Water Susceptibility. For every 5 feet the elemental moves in water, or for every gallon of water splashed on it, it takes 1 cold damage.
Multiattack. The elemental makes two slam attacks.
Slam. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 14 (2d6 + 7) bludgeoning damage plus 7 (2d6) fire damage.
Magma Boulder. Ranged Weapon Attack: +7 to hit, reach 30ft.,The elemental throws a boulder of molten rock at a creature, on a hit it takes 2d8 fire + 1d8 bludgeoning damage. The target becomes covered in molten stone and takes 1d12 fire damage each turn until it gets into contact with water, gets hit with cold damage, removes it from them, taking an additional 1d8 fire damage, or until 4 rounds have passed.
Lava Breath (Recharge 6). The elemental exhales a 30-foot cone of molten lava. Each creature in that area must make a DC 18 Dexterity saving throw, taking 55 (10d10)fire damage on a failed save, or half as much damage on a successful one. If the target is a creature or a flammable object, it ignites. Until a creature takes an action to douse the fire, the target takes 5 (1d10) fire damage at the start of each of its turns.