Hyu are ghost-like enemies found within A Link to the Past.
Hyu serve as the Dark World counterparts to the Poes that are found within the Light World. Instead of haunting the Hyrulian Cemetery though, these enemies reside in the Village of Outcasts, flying over the desolate and ruined buildings that populate the village.
Hyu will patrol back and forth, gliding through the air, just like Poes. They don't really directly attack Link, but if they come into contact with him, two full hearts of damage will be done. Link can defeat the Hyu with two slashes from his Master Sword. Alternatively, the enemy can be defeated with a number of projectile attacks including one shot from Link's Ice Rod.
While the enemies primarily are found in the Village of Outcasts, Hyu are also encountered along the pathways that lead into the Skeleton Forest.
Hyu from A Link to the Past.