Cosmos Elemental

Spirit Form. The Elemental can enter a hostile creatures space and stop there it can move through a space as narrow as 1 inch wide without squeezing.

Mental Weakness. If the Elemental take psychic damage it will be stunned for a round.

Telepathy. The Elemental can psychically communicate with anyone within 60ft

Multiattack. The Elemental makes two Elemental Power attacks.

Elemental Power. The Elemental can use any special trait or action from the other four Elementals. 

• Air: Whirlwind (Recharge 4–6). Each creature in the elemental's space must make a DC 13 Strength saving throw. On a failure, a target takes 15 (3d8 + 2) bludgeoning damage and is flung up 20 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 13 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.
• Fire: Touch. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) fire damage. 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.
• Earth: 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.
• Water: Whelm (Recharge 4–6). Each creature in the elemental's space must make a DC 15 Strength saving throw. On a failure, a target takes 13 (2d8 + 4) bludgeoning damage. If it is Large or smaller, it is also grappled (escape DC 14). 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 Large creature or up to two Medium or smaller creatures at one time. At the start of each of the elemental's turns, each target grappled by it takes 13 (2d8 + 4) 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 14 Strength check and succeeding.

Spiritual Possession. One humanoid that the Elemental can see within 10ft of it must succeed on a DC15 Charisma saving throw or be possessed by the elemental; on a fail the Elemental then disappears, and the target is incapacitated and loses control of its body. The targets can repeat the saving throw if it takes any damage. The Elemental now controls the body but does not deprive the target of its awareness. The possession lasts one hour or it will end if the creature drops to 0 hit points or the elemental can end it as a bonus action. When the possession ends, the Elemental unoccupied space within 5ft of the body. The target is immune to the Elementals possession for 24 hours after succeeding a saving throw or after The Possession ends.