Absorb Blood. After landing a successful Meele Attack on a Creature it can heal for 2d4. If the Undead Enforcer is at full Health he instead adds 1d4 as temporary hitpoints to its total HP, maxing out at a quarter of its hitpoints rounded down.

Regain Flesh. The more Health the Undead Enforcer has the more it appears to be human and the more intelligent it gets:

Over 50 HP the Undead Enforcer looks Human enough to easily blend into Human society. Commoners or Players with a Passive Perception over 15 may feel uneasy around it but can not point out why. In dim light or darkness the Undead Enforcer looks indistinguishable to a human being. Players must succeed on a DC 20 (Perception) WIS check to notice that their uneasyness stems from the Undead Brute specifically and a  DC 15 (Medicine) INT to recognise why they are unnerved around it .

At 50 HP or less the Creature only in darkness does the creature look human anymore. In dim light the same Perception and Medicine Checks as before apply in normal light however both DCs lower by 5 and Clerics, Paladins or Players who have experience with the Undead know the Undead Brute to be unalive. The Creature now knows when it is found out. Additionally its CHA now is 8 and INT 10 and all attacks that deal piercing or slashing damage against living creatures within 20ft of the Undead Enforcer heal it by 2d4.

At 25 HP: The Creature looks clearly undead now: black blood, deep wounds and injuries that no living thing can survive. With living flesh no longer weighing it down, DEX & CON increase to 25 and Movement increases to 60ft. Additionally successfull meele attacks by the Undead Enforcer now heal 2d10. It gains the following ability:
Disguise as corpse: (1 Action) A player must succeed on a DC 10 (Medicine) INT or a DC 15 (Perception) WIS check otherwise the Monster appears as a corpse.

At 10 HP or below it has INT, WIS & CHA equal to 5 and resembles a Skeleton. Its DEX and CON are their default values again, but the DC of Disguise as corpse increases by 5 for both Medicine and Perception Checks.

Undead Flaws. The Undead Enforcer has the following flaws:

Ressurected. The Power of the Undead Enforces is liked to the Necromancer it has been ressurected by. If its master is killed, the magic that keeps the creature alive fades with them.
However, if the Undead Enforcer chooses to defy its master it can set up a ritual to siphon its masters power for itself. See: Emancipation Ritual

Servant: If Enforcers Necromancer gives it a comand it has to obey this command unless it succeeds on a DC 15 WIS saving throw.

Multiattack. The Undead Enforcer makes three attacks, only one of which can be a Disorientating strike.

Claws. Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 8 (2d6 + 5) slashing damage.

Disorientating strike. Melee Weapon Attack: The Undead Enforcer brandishes its Club (previously disguised as a walking stick) dealing 2d6+5 blugeoning damage to all Creatures within 5ft. Every Player hit by this attack must succeed on a DC 15 CON saving throw or will not be able to use an action or a bonus action until the Undead Enforcers next turn.

Life Drain. Melee Attack Roll: +12, reach 5 ft. (3d6 + 5) Necrotic damage. If the target is a creature, its Hit Point maximum decreases by an amount equal to the damage taken.

Frightening Speed. The Undead Enforcer casts fear in a circle centered on himself (allies automatically succede on the saving throw). The further the Undead Enforcer can move or has moved in its last turn (what ever is greater) the higher save DC (WIS) will be 10 + 1 multiplied by every 5 ft over 30. Enemies within 10ft of it have disadvantage on that saving throw

Cold Grip. The Enforcer reaches out with one of his Hands and grasps the limb of a Player within 5ft of the Enforcer. They must succeede on a DC 15 STR saving throw or be restrained. If the targeted player is concentrating on a Spell they have to roll a concentration safe regardless if they succeed on the DC 15 STR save or not.

Self mutilation. The Creature deals itself 4d8 necrotic damage (halved due to Resistance), the next successfull attack against an enemy gets dealt the same amount (full damage unless targed also has Resistance).

Unrelenting Endurance. If the Undead Enforcer is Restrained, Grappled, Paralysed, Stunned or Exhaused it can choose to end this condition twice per day.