Rex Sacrorum

In ancient times, the political, military, and religious functions were all gathered in the hands of a single man, the King. Romulus, our first King, was in fact commander, priest, and augur as well. With the passage into the Republic and the leadership of the consuls, the religious and political/military functions were split. The responsibilities of rituals were entrusted to a religous "rex," rightly called the Rex Sacrorum, the king of sacred things. Today he is the third most important priest, after the Pontifex Maximus and the Flamen Dialis. He's part of the College of Pontiffs. The Rex Sacrorum is chosen from among the most prominent families, preferably patricians, although in theory it's not necessary for him to be noble. His is a lifetime appointment, and he is nominated directly by the Pontifex Maximus.
Like the Flamen Dialis, the Rex Sacrorum must also be born of a couple married throug the religious ritual of confarreatio. He must marry with the same rite too, as his wife will share with him part of his sacred tasks and will take the title of Regina Sacrorum. The Rex always carries with him a sacred ax, and the regina wears a crown of pomegranate twigs entwined with wool ribbons. The Rex and Regina continuously perform fixed sacrifices, to maintain the Empire under a constant magical-religious coverage. On the kalendae, the Rex offers sacrifices to Janus and the Regina to Fortuna. On the nonae, the Rex's sacrifices are to Jupiter and the Regina's to Juno. On the ides, the Rex offers a sacrifice to Mars and the Regina to Bellona. In case the augurs detect negative omens or threats to the Pax Deorum, the Rex immediately performs a series of rituals to placate the gods, while the Regina goes to offer sacrifices together with the vestals.