Horde. The horde can occupy another creature's space and vice versa, and the horde can move through any opening large enough for a Medium zombie- though it will take a full movement turn to do so. Additionally, the horde is immune to any spell or effect that would alter its form.

Reactive. The horde can take one reaction on every turn in combat.

Stampede. When the horde moves through the space of a Large or smaller creature, the horde can force the creature to make a DC 14 Strength saving throw. On a failed save, the creature is knocked prone.

Turn Resistance. The horde has advantage on saving throws against any effect that turns undead. Additionally, the horde can be affected by the Destroy Undead feature regardless of CR limits, but has advantage on the saving throw against it and is not destroyed on a failed save. Instead, it takes radiant damage equal to 5 × the cleric's level on a failed save, or half as much damage on a success.

Undead Fortitude. If damage reduces the horde to 0 Hit Points, it must make a Constitution saving throw with a 5+ half the damage taken, unless the damage is radiant or from a critical hit. On a success, the horde drops to 0 hit points, then regains 22 hit points as several zombies previously thought dead rise to fight again.

Multiattack. The horde makes two slam attacks, or one slam attack if the horde has half its hit points or fewer.

Slam. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 14 (2d6 + 8) bludgeoning damage, or 1d6+4 if the horde has half its hit points or fewer.