Combined Elemental

Earth Glide.  The elemental can burrow through nonmagical, unworked earth and stone. While doing so, the elemental doesn't disturb the material it moves through.

Fire Form. A creature that touches the elemental or hits it with a melee attack while within 5 feet of it takes 5 (1d10) fire damage. In addition, the elemental can enter a hostile creature's space and stop there. The first time it enters a creature's space on a turn, that creature takes 5 (1d10) fire damage and catches fire; until someone takes an action to douse the fire, the creature takes 5 (1d10) fire damage at the start of each of its turns.

Illumination. The elemental sheds bright light in a10-foot radius and dim light in an additional 10 feet.

Malleable Form. The elemental can enter a hostile creature's space and stop there. It can move through a space as narrow as 1 foot wide without squeezing.

Siege Monster. The elemental deals double damage to objects and structures.

Multiattack. The Combined Elemental makes three slam attacks.

Slam. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 13 (2d6 + 6) bludgeoning damage plus 11 (2d10) fire damage. 

Cyclone (Recharge 5–6). Each creature in the elemental's space must make a DC 16 Strength saving throw. On a failure, a target takes 22 (4d8 + 4) bludgeoning damage and is flung up 30 feet away from the elemental in a random direction and knocked prone. If a thrown target strikes an object, such as a wall or floor, the target takes 3 (1d6) bludgeoning damage for every 10 feet it was thrown. If the target is thrown at another creature, that creature must succeed on a DC 16 Dexterity saving throw or take the same damage and be knocked prone.

If the saving throw is successful, the target takes half the bludgeoning damage and isn't flung away or knocked prone.

Overwhelm (Recharge 5–6). Each creature in the elemental's space must make a DC 16 Strength saving throw. On a failure, a target takes 19 (3d8 + 5) bludgeoning damage. If it is Large or smaller, it is also grappled (escape DC 15). Until this grapple ends, the target is restrained and unable to breathe unless it can breathe water. If the saving throw is successful, the target is pushed out of the elemental's space.

The elemental can grapple one Huge creature or up to two Large or smaller creatures at one time. At the start of each of the elemental's turns, each target grappled by it takes 19 (3d8 + 5) bludgeoning damage. A creature within 5 feet of the elemental can pull a creature or object out of it by taking an action to make a DC 15 Strength check and succeeding.