Zombie Corrupter

Zombie Corrupter

Large undead, chaotic evil

Armor Class: 15

Hit Points: 76

Speed: 28 ft , fly: 28 ft , can hover

STR

15 +2

DEX

15 +2

CON

16 +3

INT

7 -2

WIS

12 +1

CHA

5 -3

Saving Throws: Constitution +7, Strength +5

Skills: Perception +3
Undead Fortitude
If damage reduces the corruptor 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, it drops to 1 hit point instead.

Damage Vulnerabilities: Radiant

Damage Resistances: Cold, piercing, slashing

Damage Immunities: Poison

Condition Immunities: Poisoned

Senses: Senses blindsight 90 ft., passive Perception 13

Languages: Common, Elven

Undead Nature. A corruptor doesn't require air, food, drink, or sleep.
Undead Self Destruct - 
If the Zombie corrupter is close to death it is possible it will trigger it's viral explosion and self destruct.  Every living creature within a 50 ft. radius must make a constitution saving throw DC 12.
On a fail the creature is poisoned, if this condition is not reversed that creature will become a zombie in one minute.

Actions

Bite
Melee Weapon Attack:
+6 to hit, reach 5 ft., one target. Hit: 12 (2d8 + 3) piercing damage, and the target must make a DC 12 Constitution saving throw, taking 10 (1d20) poison damage on a failed save, or half as much damage on a successful one.
Spit
Ranged Weapon Attack: +6 to hit, range 40/80 ft.,
one creature or two creatures that are within 5 feet of each other. Hit: 16 (3d10) acid damage, and the target must make a successful DC 12 Constitution saving throw or be poisoned for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

If the effect is not reversed, after 1 minute the target turns into a zombie.  The body dies and an undead creature rises instead. 

The Zombie corrupter is a person with an innate resistance to the magical virus that creates zombies.  At first this may seem like a good thing, but the person is now a carrier.  Unknowingly spreading the virus amongst populations of towns or even cities.  The virus works slower but more methodically, the dead now rise after a few days shambling forward to eat victims.  Without clear evidence back to the carrier.  
The Corrupter is created when a carrier is killed and reanimated by a vampire or equally devious villain.  They strengthen the newly undead carrier and can use this new creature to infect large swaths of people incredibly quickly.