Prior to becoming commander of the Dark Blade Legion, DeMeer gallantly served under Colonel Maureen York and was a contemporary of Sergeant Squall Chitose, a future member of the Eidola Pirates. On Year 4 Day 133, Vodo Bonias deposed Charon as emperor and installed Greyson Uebles as his puppet on the Imperial throne. Believing Uebles to be unfit to serve as emperor, Mark DeMeer and most of his loyal legionnaires departed the Galactic Empire. One of DeMeer's subordinates, Sergeant First Class (E-7) Konar Siosk-Baas, was later caught and killed by the Eidola Pirates.