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.

Infection. When a character is bitten they must make a constitution saving throw of 15 to see if they contract the plague. Nat 1 they immediately contract the plague and turn falling under dm control. 5 or lower they have 2 days to cure it, 6-10 they have 5 days, 11-14 they have a week. the only ways to cure it is to either cut off the area of infection within the hour and risk fighting massive blood loss (1d6 - con bleeding damage) or they can find someone who can cast the lesser restoration. Important when a character dies while infected they immediately turn unless spare the dying was cast on them while they made saving throws. 

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

Claw. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 4 (1d4 + 1)  slashing damage.

Bite. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 4 (1d8 + 1)  piercing damage.