Cerberus Zombie

 Aggressive. As a bonus action, the cerberus zombie can move up to its speed toward a hostile creature that it can see.

Multiheaded. The cerberus zombie can't be surprised, and it has advantage on saving throws against being knocked unconscious.

Pack Tactics. The cerberus zombie has advantage on an attack roll against a creature if at least one of the cerberus's allies is within 5 feet of the creature and the ally isn't incapacitated.

Disgorge Zombie. As a bonus action, the cerberus zombie can disgorge a normal zombie, which appears in an unoccupied space within 10 feet of it. The disgorged zombie acts on its own initiative count. After a zombie is disgorged, roll a d6. On a roll of 1, the cerberus zombie runs out of zombies to disgorge and loses this trait. If the cerberus zombie still has this trait when it dies, 1d4 normal zombies erupt from its corpse at the start of its next turn. These zombies act on their own initiative count.

Undead Fortitude. If damage reduces the cerbeus zombie to 0 hit points, it must make a Constitution saving throw with a DC of 5+the damage taken, unless the damage is radiant or from a critical hit. On a success, the zombie drops to 1 hit point instead.

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) piercing damage plus 3 (1d6) necrotic damage.

Breath Weapon (Recharge 5–6). The cerberus zombie exhales shadowy mist in a 30-foot cone. Each creature in the cone must make a DC 16 Constitution saving throw. On a failed save, the creature take 21 (6d6) cold damage and is frightened of the cerberus zombie until the end of the cerberus zombie's next turn. On a successful save, the creature takes half as much damage and isn't frightened.