Multiattack

Two Slam attacks. If both attacks hit a Med or smaller target the target is grappled (escape DC 13).

Slam

Melee Weapon Attack: +5 to hit, 5 ft., one target, 10 (2d6+3) bludgeoning damage.

Grind

Grinds its form over one creature in its space or that is grappled by it. Target takes 21 (6d6) bludgeoning damage (DC 13 Dex half). Flow regains hp equal to half the damage taken if creature is not a Construct or Undead.