Bite. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 3d10 + 6 piercing damage.

Constrict. Melee Weapon Attack: +10 to hit, reach 5 ft., one Large or smaller creature. Hit: 2d10 + 6 bludgeoning damage plus 2d10 + 6 slashing damage. The target is grappled (escape DC 16) if the undead behir isn't already constricting a creature, and the target is restrained until this grapple ends.

Death Breath (Recharge 5–6). The undead behir exhales a line of noxious gas that is 20 feet long and 5 feet wide. Each creature in that line must make a DC 15 Constitution saving throw, taking 12d10 necrotic damage on a failed save, or half as much damage on a successful one.

Lightning Breath (Recharge 5–6). The undead behir exhales a line of lightning that is 20 feet long and 5 feet wide. Each creature in that line must make a DC 16 Dexterity saving throw, taking 12d10 lightning damage on a failed save, or half as much damage on a successful one.

Reanimation. The undead belier releases a burst of necrotic electricity that feels like a chill down the spine to anyone living but reanimates any flesh creature whose corpse is still in tact within reason. It becomes an undead creature that is chaotic evil towards anyone but the undead behir.