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.

Telepathic Bond.  Xyoddin has a permanent telepathic bond with Azaven. 

Brain Consumption. When Xyoddin makes a successful grapple check to deal damage with his bite against a pinned or helpless living foe, the victim takes 2d4 points of Intelligence drain as Xyoddin consumes portions of his brain.
A successful DC 23 Strength save halves this Intelligence drain. A creature reduced to 0 Intelligence by this attack is slain. Creatures immune to critical hits and those with multiple heads are not killed by this attack.

Favored Prey.  Xyoddin gains a +2 bonus on damage rolls against humanoids and a +2 bonus on Persuasion, Perception, Insight, and Survival checks when using these skills against humanoids.  Against humans, these bonuses increase to +4.

Unnatural Aura.  Any animal within 30 feet of Xyoddin must succeed at a DC 18 Wisdom save or become panicked, remaining so for as long as it remains within this proximity. This is a mind-affecting fear effect.

Command Zombies.  Xyoddin can automatically command all normal zombies within 30 feet as a free action. Normal zombies never attack him unless they are compelled.

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

+1 Human Bane Dagger. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 4 (1d6 + 8) piercing damage.

Sprint.  Once per day, as a bonus action, Xyoddin can move at a speed of 300 feet when he makes a charge.

Cannibalistic Healing.  So long as Xyoddin has fed on human flesh within the last 24 hours, as a reaction he can gain 10 hp when he is successfully damaged by an enemy.