Cordyceps

Undead Fortitude. If damage reduces the cordyceps 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.

Infection. Every successful attack made by this monster is accompanied by a 5% chance of becoming infected with Cordyceps. A DC 12 Insight check will reveal the cure to be a potion made from a greater healing potion and a fleshrot poison. This disease consists of six stages: 1) +2 CON & -2 INT   2) +2 STR & character's alignment shifts to Chaotic, or to Evil if already Chaotic   3) +2 CON & -2 INT, character becomes obsessed with protecting fungi   4) +2 STR & -4 INT character's alignment becomes Chaotic Evil   5) +4 CON & -4 INT, CHA, & WIS in addition to fugal growths appearing on the character   6) Character dies and becomes a Cordyceps that can wield the weapons, armor, and spells of the character.

Slam. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 9 (1d6 + 5) bludgeoning damage.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 9 (1d6+5) bludgeoning damage and 2 (1d4) poison damage.