Immutable Form. The elemental is immune to any spell or effect that would alter its form.

Magic Resistance. The elemental has advantage on saving throws against spells and other magical effects.

Magic Weapons. The elemental's weapon attacks are magical.

indomitable Form. the elemental is immune to any spell or effect that would imped its movement in any way.

Multiattack. The elemental makes two colossal slam attacks and one earthquake attack.

Colossal Slam. Melee Weapon Attack: +15 to hit, reach 15 ft., one target. Hit: 36 (4d12 + 6) bludgeoning damage.

Slow (Recharge 5–6). The elemental targets one or more creatures it can see within 10 feet of it. Each target must make a DC 17 Wisdom saving throw against this magic. On a failed save, a target can't use reactions, its speed is halved, and it can't make more than one attack on its turn. In addition, the target can take either an action or a bonus action on its turn, not both. These effects last for 1 minute. A target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Earthquake.  the elemental casts earthquake.

Earth Shatter. (once every three rounds) Melee Weapon Attack: +15 to hit, reach 50 ft., one target. Hit: 42 (7d12 + 6) bludgeoning damage.