Undead Fortitude. If damage reduces the 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.

Infectious Corruption. When the zombie critically hits with a bite attack, the target must make a Dexterity or Strength Saving Throw DC 5, on a failed save target contracts the pathogen. On a successful save, nothing happens and for every one following the DC increases by 5. DC resets at the end of combat.

Frankestien Abominations. This creature can consume organic creatures, alive or dead, and once enough has been eaten, the creature may grow a set of jagged appendage like limbs that it detaches from itself to create new monsters. How it imbues these creatures with sentience is unknown.

Slam. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 4 (1d6 + 1) bludgeoning damage.

Bite. Melee Weapon Attack: +0 to hit, reach 5 ft., one target. Hit:  5 (1d8 +2) piercing damage. Str/Dex Save DC 5 x # of previous bites.

Impale. Melee Weapon Attack: +3 to hit, reach 10 ft., one target. Hit: 12 (2d8+4) peircing damage.