Mob of Zombies (5e Creature)
From D&D Wiki
Mob of Zombies
Gargantuan swarm of Medium undead, neutral evil
Saving Throws Wis +2
Mob. The mob of zombies can occupy another creature's space and vice versa, and the mob can move through any opening large enough for a Medium zombie. The mob can't regain hit points or gain temporary hit points.
Undead Fortitude. If damage reduces the mob to 0 hit points, it must make a Constitution saving throw with a DC equal to the damage taken, unless the damage is radiant or from a critical hit. On a success, the mob drops to 1 hit point instead.
Slams. Melee Weapon Attack: +10 to hit, reach 0 ft., all target's in the mob's space. Hit: 20 (4d6 + 6) bludgeoning damage. If the target is a creature, it is also grappled (escape DC 17).
A mob of zombies is a densely packed swarm of zombies, tearing everything in its path apart and leaving a trail of destruction in its wake. The sheer number of zombies working in unison can be a difficult challenge for even the best-prepared slayers of undead.