mystery

noun

• Something secret or unexplainable; an unknown.

  "The truth behind the events remains a mystery."

• Someone or something with an obscure or puzzling nature.

  "That man is a mystery."

• A secret or mystical meaning.
• A religious truth not understandable by the application of human reason alone (without divine aid).
• (obsolete outside Eastern Orthodoxy) A sacrament.
• (chiefly in plural) A secret religious celebration, admission to which was usually through initiation.

  "the Eleusinian mysteries"

• A particular event or series of events in the life of Christ.

  "The second decade of the Rosary concerns the Sorrowful mysteries, such as the crucifixion and the crowning with thorns."

• A craft, art or trade; specifically a guild of craftsmen.