Please answer a question about the following article about The Legend of Zelda: Twilight Princess:

When Link enters the Twilight Realm, the void that corrupts parts of Hyrule, he transforms into a wolf.[h] He is eventually able to transform between his Hylian and wolf forms at will. As a wolf, Link loses the ability to use his sword, shield, or any secondary items; he instead attacks by biting, and defends primarily by dodging attacks. However, "Wolf Link" gains several key advantages in return—he moves faster than he does as a human (though riding Epona is still faster) and digs holes to create new passages and uncover buried items, and has improved senses, including the ability to follow scent trails.[i] He also carries Midna, a small imp-like creature who gives him hints, uses an energy field to attack enemies, helps him jump long distances, and eventually allows Link to "warp" to any of several preset locations throughout the overworld.[j] Using Link's wolf senses, the player can see and listen to the wandering spirits of those affected by the Twilight, as well as hunt for enemy ghosts named Poes.[k]

Hostile spirits are also known as what?
Poes