Oath: 1. To make an undertaking or swear to do something or serve someone.
2. A spoken witness that a statement is true or a promise shall be kept.
Offering: To present goods, or a victim in way of sacrifice, to a god or deity.
Ogre: Man-eating giant in folklore.
Old Nick: The devil.
Omen: Occurrence that predicts or prophesises a good or evil happening.
Oppress, Oppression: 1. Govern or treat somebody cruelly or unjustly.
2. Weigh somebody down with worry or sadness.
Ordeal: 1. Ancient mode of deciding a person innocence or guilt by subjecting them to a physical test.
2. Experience that tests character or endurance.
Outcast: Person cast out or cut off from home and family, homeless of friendless.
Outlaws: Person deprived of the protection of the law or operating outside the law.