Pile of Corpses. The Zombie Amalgam is made up of multiple zombies, the amount of zombies is referred to as the pile count (the default statblock assumes a pile count of 5). The maximum hit points of the Zombie Amalgam is equal to 22 x the pile count. For every 22 hit points lost, the pile count decreases by 1 which in turn reduces the maximum hit points by that many. When the pile count reaches 1, the Zombie Amalgam stats change to that of a regular zombie.

Undead Fervor. The Zombie Amalgam gets a number initiative rolls equal to its pile count. Each time the pile count decreases, it loses its lowest initiative roll. If it loses the initiative roll during the corresponding turn, it's turn immediately ends.

Note: Instead of rolling each individual initiative check, you can instead split the number of rolls evenly between 18 and -2. (ie for a pile count of 5, the rolls would be 18, 13, 8, 3, -2).

Necromantic Cohesion. Whenever the Zombie Amalgam takes damage, after applying any reductions to the pile count, 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, which counts as a guaranteed failure. On a failure, reduce the pile count by 1 and create a zombie in an adjacent space to the Zombie Amalgam with current hit points equal to the amount of life lost from reducing the pile count. The zombie created takes over the initiative order that reducing the pile count lost for the Zombie Amalgam.

Any conditions in effect on the Zombie Amalgam are also applied to the newly created zombie. Any spells in effect on the Zombie Amalgam also apply to the newly created zombie, even if the spell wouldn't normally be able to target/affect multiple creatures. The newly created zombie makes its own saving throws on its own initiative if any are required. Any spell cast or effect applied after the zombie is created treat the new zombie as a separate creature.

Multiattack. The Zombie Amalgam makes two Slam attacks. It can only use this action if it hasn't spent any movement this turn. If the same creature is hit by both Slam attacks, the target is Grappled (escape DC 13).

Slam. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) bludgeoning damage.