Turn Immunity. The swarm is immune to effects that turn undead.

Swarm. The swarm can occupy another creature's space and vice versa, and the swarm can move through any opening large enough for a Tiny crawling claw. The swarm can't regain hit points or gain temporary hit points.

Claw. Melee Weapon Attack: +5 to hit, reach 5 ft., one target within the swarm’s space. Hit: 7 (2d4 + 2) bludgeoning or slashing damage (swarm’s choice), or 5 (1d4 + 2) bludgeoning or slashing damage (swarm’s choice) if the swarm is at half of its hit points or fewer.

Grab (Recharge 5-6). A creature within the swarm’s space must succeed on a DC 12 Strength saving throw or be grappled by the swarm. A creature grappled in this way may retry this save at the end of each of their turns for as long as the condition lasts. The condition ends when the swarm lets go, or when the creature succeeds on a save.