Although fearsome in appearance Oni are the dual natured
Japanese creatures of legend that represent both the
demonic "destroyer" and the
godlike "protector".
The Shinto Oni was originally more god than demon but the perception of these helpful spirits changed to become gradually more mischievous. They became associated with misfortune (analogous to storm gods) and later became incorporated into the new Buddhist concept of Hell. Oni became the guardians of Hell, torturing and collecting the souls of the wicked, swooping down from the sky to take them from those who are about to die.
Aspects of the protector side are still apparent with many traditional Japanese houses having a tile shaped like an Oni's face (known as Oni-gawara) placed on the roof to protect the home from evil.
Many festivals are led by marchers wearing Oni masks who walk before the processions, driving away any evil spirits.