Water Wraith

Intangible- The Water Wraith is in the Ethereal Plane. It is immune to all damage while it is in this plane. If you hit the Water Wraith with Psychic, Radiant, or Force damage it exits the Ethereal Plane. It renters at the start of its next turn

Multiattack. When Water Wraith takes the attack action can use two Slam or Charge Attacks.

Slam. Melee Weapon Attack: +7 to hit, reach 10 ft., 1 target. Hit: 15 (2d10 + 4) Bludgeoning damage. 

Charge. Melee Weapon Attack: +7 to hit, The Water Wraith charges forward in a straight line, running over all of the creatures in the path of it dealing 11 (2d6 + 4) Bludgeoning damage, and forcing the creature hit to make a Dex. Saving Throw (DC. 14) or be knocked prone

Pull- Range/30 ft. The Water Wraith extends out its arm and pulls you toward it. The creature must make a DC 14 Str. Saving Throw or be pulled up to 10 feet toward the Water Wraith.