The Sons of Caligula

From publisher blurb:

Marcus Julius Maximus, a respected member of the Roman aris- tocracy, asks for an official mission of the Cohors Arcana. After beeing selected, the Custodes are sent by their commander to a mid- night meeting at Maximus’ villa. The official explains them he is a senior member of a powerful secret society that most have only heard vague whispers about, often supporting the Cohors. That night under the cover of darkness, he explains to them that in the Hellespont an evil conspiracy has been brewing for decades. That “Sons of Caligula” cultists may have found the location of the lost Sceptre of Atlas, thought lost under the ochre waves of the Pontus Euxinus (the Black Sea) in the famous sunken city of Atlantis.