Udah

Udah the Undying was a male lich-turned-demilich that haunted the Tomb of Udah, a large necropolis in the Dreamseep Marshlands of Tal'Dorei.

Description
Udah savored the torment he inflicted upon greedy individuals who entered the Tomb of Udah. As a demilich, according to rumor, he was a three-eyed golden skull with a ruby in each socket.

History
Udah the Undying was a male individual who was once a lich of tremendous power that, by 812 PD, had faded into a demilich. His resting place was the Tomb of Udah, a large necropolis in the Dreamseap Marshlands filled with traps and treasure, that claimed the lives of hundreds of treasure hunters and grave robbers, with each death adding to the legions under Udah's control.

Two rumors persisted in Tal'Dorei regarding the Tomb of Udah: one of a three-eyed golden skull, with a wish-granting ruby in each socket, and a second of a "dread master" that commanded the monsters in the necropolis. Unbeknownst to the spreaders of these rumors, in reality, the skull and the master were the same entity.

Demilich abilities

 * Natural armor — Udah possessed natural armor, granting him an armor class of 20.
 * Speed — Udah could not move normally but possessed a hovering speed of 30 feet per turn.
 * Saving throws — Udah was proficient in Constitution, Intelligence, Wisdom, and Charisma saving throws.
 * Damage resistances and immunities — Udah was resistant to bludgeoning, piercing, and slashing damage from magic weapons and immune to bludgeoning, piercing, and slashing damage from nonmagical attacks. He was also immune to necrotic, poison, and psychic damage.
 * Condition immunities — Udah could not be charmed, deafened, exhausted, frightened, paralyzed, petrified, poisoned, prone, nor stunned.
 * Senses — Udah possessed truesight out for 120 feet, as well as a passive Perception of 13.
 * Avoidance — If Udah was subject to an effect that allowed him to make a saving throw to take half damage, he only took half damage upon failure and no damage on a success.
 * Legendary Resistance — Thrice per day, should Udah fail a saving throw, he could choose to succeed instead.
 * Turn immunity — Udah was immune to effect that turned undead.
 * Actions:
 * Howl — Udah could let out a howl that forced creatures within 30 feet to make a Constitution saving throw or drop unconscious. Creatures that succeeded were temporarily frightened of him. This ability required recharge.
 * Life Drain — Udah could target up to three creatures within 10 feet, forcing them to make a Constitution saving throw or take a large quantity of necrotic damage, healing the demilich an equal amount.
 * Legendary Actions:
 * Flight — Udah could fly up to half its flying speed.
 * Cloud of Dust — Udah could magically swirl its dusty remains, forcing creatures within 10 feet to make a Constitution saving throw or be temporarily blinded. Creatures that succeeded the saving throw were temporarily immune to the ability.
 * Energy Drain — Using two Legendary Actions, Udah could force creatures within 30 feet to make a Dexterity saving throw or force their hit point maximum down, killing any creature that gets knocked out. Hit point maximums could be restored with Greater Restoration or similar magic.
 * Vile Curse — Using three Legendary Actions, Udah could target one creature within 30 feet to make a Wisdom saving throw or become cursed; until the curse ended, the target had disadvantage on saving throws and attack rolls, but they could repeat the save at the end of each of their subsequent turns.