Swarm. The swarm can occupy another creature's space and vice versa, and the swarm can move through any opening large enough for a small insect. The swarm can't regain Hit Points or gain temporary Hit Points. Leech. while the swarm has a creature grappled, that creature loses 2d10+2 hit points at the start of its turn.
Bite. Melee weapon attack: +3 to hit, reach 0ft., one target in the swarm's space. Hit: 2d4 piercing damage, or 1d4 if the swarm has less than half of its maximum hit points remaining. Creatures that take damage from this attack become grappled.