Undying. After this creatures hp falls to 0 by any damage other than radiant it becomes incapacitated and will rise again in 1d10 days.

Radiant Damage at will disintegrate whatever part of the body it hits.

Bonus action. As a bonus action to a successful grapple Xenithor's cursed can also bite with additional +3 to attack.

Grapple. (1 action): Xenithor's Cursed tries to grapple the nearest living target. That target must make a DC15 STR, or DEX save or become grappled.

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., 1 target. Hit: 5 (1d6 +4) piercing damage and 7 (1d10 +4) necrotic damage. 

Bile. Ranged  Projectile Attack: +4 to hit, range 5/15 ft. cone,  Hit: 7 (1d10 +4) necrotic damage.