Swarm. The horde can move through any opening large enough for a Medium humanoid. The horde can't regain hit points or gain temporary hit points.

Undead Swarm Fortitude. When the swarm reaches 0 hit points it is destroyed. When destroyed 1d6 zombies appear at half health in the hordes place.

Power in Numbers. When the horde reaches half its health, the damage of its attacks is reduced (included in attacks).

Multiattack. The horde can make three attacks, only one of which can be pull under.

Gnaw and Claw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 18 (4d6 + 4) piercing damage or 11 (2d6 + 4) piercing damage if the horde has less than half its maximum hit points.

Pull Under. Melee Weapon Attack: + 7 to hit, reach 5 ft., one target. Hit: 18 (4d6 +4) piercing damage or 11 (2d6 + 4) piercing damage if the horde has less than half its maximum hit points, on a hit, the target must also succeed on a DC 15 Strength saving throw or be pulled into the hordes space. While in the hordes space the target is restrained and moves with the horde. The target can make a DC 15 Strength saving throw at the end of its turn to try and break free, moving to a free space beside the horde.