Mysteries of Eleusis. Illustration after a scene on an amphora of Vulci in the British Museum. Scene depicts an initiation. The priests of Eleusis were selected at 12 or 14 by lot from among the Eupatrids. The lad designated remained in charge of the altar. Annually, at the celebration of the Eleusinian mysteries, a new person was initiated. The office was considered a sacred ministry.