Ancient Dragon Zombie

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.

Multiattack. The zombie can use its Frightful Presence. It then makes two attacks: one with its bite or tail, and once with its claw.

Bite. Melee Weapon Attack: +16 to hit, reach 10 ft., one target. Hit: 21 (2d10 + 10) piercing damage.

Claw. Melee Weapon Attack: +16 to hit, reach 5 ft., one target. Hit: 17 (2d6 + 10) slashing damage.

Tail. Melee Weapon Attack: +12 to hit, reach 15 ft., one target. Hit: 19 (2d8 + 10) bludgeoning damage.

Frightful Presence. Each creature of the zombie's choice that is within 120 feet of the zombie and aware of it must succeed on a DC 17 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the zombie's Frightful Presence for the next 24 hours.

Baleful Breath (Recharge 5-6). The zombie exhales pestilent gas in a 60-foot cone. Each creature in that area must make a DC 23 Constitution saving throw, taking 66 (12d10) necrotic damage on a failed save, or half as much damage on a successful one.