Undead Fortitude. If damage reduces the Necrolyte to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is Acid or from a critical hit. On a success, the Necrolyte drops to 2 hit points instead.   Necrotic Absorption. Whenever the Necrolyte is subjected to necrotic damage, it takes no damage and instead regains a number of hit points equal to the necrotic damage dealt.   Decapitate. When attacking a stunned or restrained creature and a 10 or higher is rolled for damage, the Necrolyte can attempt to behead the creature.
1d20-2 , DC 10+the creatures hit die type. The creature is beheaded on a success, but only takes half damage from the attack on a fail.