Soul Sense. The YuYu can magically sense the presence of any living creature's soul up to 1 mile away. It knows the general direction they're in but not their exact locations.

Soul of a YuYu. A creature that looks at the YuYu while in the ethereal plane, or by using magical sight such as truesight or divine sense sees its cursed, deformed soul appearing as a blackened, warped husk with a piercing blue gaze. The creature must immediately succeed on a DC 17 Wisdom saving throw or be afflicted with the YuYu's Curse.

YuYu's Curse. A creature afflicted with this curse no longer requires food or drink to survive, doesn't need to breathe, and cannot sleep. At the end of each night, the creature suffers one level of exhaustion, and its soul begins to warp, granting it the Soul of a YuYu feature. If a creature dies while under the effect of this curse, their body disintegrates, leaving behind carried items, and can only be brought back to life by a True Resurrection or Wish spell. A dead afflicted creature will resurrect into the YuYu in 1d4 days. A Remove Curse or Greater Restoration spell cast before the afflicted creature dies will lift the curse.

Multiattack. The YuYu makes three attacks with its claws.

Claws. Melee Weapon Attack: +12 to hit, reach 15ft., one target. Hit 19 (2d10+8)

 Howl (1/Day). The YuYu emits a baleful howl. This howl has no effect on creatures without a soul or any creature currently afflicted with the YuYu's Curse. All other creatures within 30 feet of the YuYu that can hear it must make a DC 17 Wisdom saving throw. On a failure, a creature drops to 0 hit points. On a success, a creature takes 35 (10d6) psychic damage.