Demise
The remaining emperor of the family of Constantine I, Constantius II broke off his war in Syria with Persia, and marched west. Despite Magnentius' efforts to gain Vetranio to his cause, the old general reached Constantius with his army, and resigned the crown.
After electing Magnus Decentius (probably his brother) to Caesar and gathering as many troops as possible, the armies of Magnentius and Constantius met in the Battle of Mursa Major in 351; Magnentius led his troops into battle, while Constantius spent the day of battle praying in a nearby church. Despite Magnentius' heroism, his troops were defeated and forced to retreat back to Gaul.
As a result of Magnentius' defeat, Italy ejected his garrisons and rejoined the loyalist cause. Magnentius made a final stand in 353 in the Battle of Mons Seleucus, after which he committed suicide by falling on his sword.
Following the suppression of Magnentius' rebellion, Constantius commanded an investigation be made to find his followers. The most notorious agent in this search was the primicerius notariorum Paulus Catena.
Some sources state that Magnentius' father was a Briton and his mother a Frank.
Read more about this topic: Magnentius