Wrackwraith

Incorporeal Movement. Move through others/objects as difficult terrain. Takes 5 (1d10) force if it ends turn in object.

Wrack Form. While animating a pile of wrack has AC 18 and can use Slam and Deluge actions. Also loses its immunity to grappled and restrained conditions and can't fly. If it moves through a creature or object with Incorporeal Movement while animating wrack wrack falls off its ghostly body ending this. Otherwise can end this as bonus action. If it takes 15+ damage in single turn while animating wrack must make DC 13 Con save or be ejected from wrack ending this.

Ghostly Touch. Melee Weapon Attack: +5 to hit, 5 ft., one target, 7 (1d8+3) necrotic.

Slam (Wrack Form Only). Melee Weapon Attack: +5 to hit, 5 ft., one target, 10 (2d6+3) bludgeoning damage + 4 (1d8) necrotic. If target is Large or smaller grappled (escape DC 13). Until grapple ends target restrained and wrackwraith can't use its Slam or attack another. Target can't breathe or speak until grapple ends.

Animate Wrack. Animates wrack within 5 ft. of it pulling the debris into a protective covering over its ghostly body.

Deluge (Wrack Form Only). Fills lungs of one creature it is grappling with seawater algae and tiny ocean debris harming creatures that breathe air or water: 14 (4d6) necrotic and chokes as lungs fill with water and debris (DC 13 Con half damage not choking). Choking creature can re-save at end of each of its turns success ends effect on itself.

Wrack Jump (Recharge 4-6). Leaves current pile magically teleports to another within 60' of it and uses Animate Wrack.