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 limb. The swarm can't regain hit points or gain temporary hit points.

Unusual Nature.

The swarm doesn't require air, food, drink, or sleep.

Actions

Multiattack.

The swarm makes one Undead Mass attack and one Grasping Limbs attack.

Undead Mass.

Melee Weapon Attack: +4 to hit, reach 0 ft., one target in the swarm's space. Hit: 5 (1d6 + 2) bludgeoning damage, or 4 (1d4 + 2) bludgeoning damage if the swarm has half of its hit points or fewer.

Grasping Limbs.

Melee Weapon Attack: +4 to hit, reach 0 ft., one creature in the swarm's space. Hit: 7 (2d6) necrotic damage, and the creature must succeed on a DC 12 Strength saving throw or be restrained. The creature can repeat the saving throw at the end of each of its turns, taking 7 (2d6) necrotic damage on a failed save. The creature is freed if it succeeds on this saving throw, the swarm moves out of the creature's space, or the swarm dies.

Swarm of Zombie Limbs