Trophonius

A son of Erginus, king of Orchomenus, or of Apollo. He with his Agamedes built the temple of Apollo at Delphi. They are also said to have constructed a treasure chamber for the Boeotian ruler Hyrieus.1

After his death he was deified as chthonic deity who resided in a cave near Levadia in Boeotia, where he had a celebrated oracle. After performing various rites, people would descend into the cave where they would receive oracular sayings in their sleep. The oracle was said to be so awe inspiring that those who entered and consulted it would never smile again.