Anerátio

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.

Aberrant Scar. The wounds conquered in battle not only scars you but also, if  "bad" enough, cause mutations on you fisical form as an attempt of healing/surviving its effects. 
 In case of receiving damage  equal or higher to your maximum hp, the creature must suceed a CON saving throw of DC 15 to take reduced damage (1d8 -3  educed from the original damage) and suffer a mutation (roll a d20 and  pick the respective mutation from the list) or take the original damage.
* The mutation effect can only ocur  4 times a year, in a moment of your choice.

 List of mutations:

Grow an extra eye
Grow a big eye with yellow iris and  visible veins 
Grow arachnid  eyes 
Grow skeletal spider-like limbs (+1 DEX or +1d20 movement speed)
Grow a stinger 
Grow a dental arcade (in case already having one, having your teeths replaced for fangs) 
Acquire a thicker skin (+1 to AC)
Grow feathers (+5 fly movement)
Grow pedipalps 
Grow an pseudo brain (gain the ability to cast mage hands)
Loose sight and gain tremor-sense
Grow claws (aquires claw atacks -> +1 to hit, 3 (1d6) slashing damage)
Grow antlers (aquires antler atacks -> +1 to hit,  4 (1d8 -1) piercing or bludgeoning damage)
Double upper limbs (up to the DM's imagination)
Double lower limbs (adavantage "against being prone")
Grow wings (+1d20 movement speed)
Grow tentacles (+1 extra atack during your action)
Grow hull (+2 AC)
Serpentine body (+2DEX)
Exoeskeleton (+1 AC)
Aberrant Albinism (Able to cast the light cantrip)
Grow another head (multiatack: realises 2 bite atacks)

Innate Spellcasting. The Anerátio spellcasting ability is Intelligence (spell save DC 14). It can innately cast the following spells, requiring only verbal components:

At will: hex

3/day each: expeditious retreat (self only)

1/day each: Cause FearConcentration

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

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

expeditious retreat (self only)

according to innate spellcasting rules

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