Yūrei

Yūrei (幽霊, or ゆうれい) is an enemy in Wario Land 4. It is a large pirate ghost that roams around outdoor areas of the level Crescent Moon Village, searching for treasure. It flies around pursuing Wario and cannot be defeated. It will steal any coin it can get in greed. Also if Wario has the key like ghost, Yūrei will also try to snatch it away as well. If it succeeds, it will laugh and all doors will be locked until Wario recovers it back.