Opus Dei is a Bunker City, and the summer quarter of the travelling Black Magic Circus, a Magic Academy. It is protected by Fley of the Tribe of Phex, which is lead by Nostraphex. A large amount of magic students keeps living in Opus Dei through the winter. Only those the Ringmaster Julius Esterhazy deems able to defend themselves and/or useful in the circus acts and mercenary missions travel with the Circus. As such, winter is generally considered "holiday time" for the pupils as most of the teachers are gone travelling.