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Magnentius was a Roman general and usurper who ruled from 350 to 353. He initially served under Constantius II, but rebelled against him in 350 after Constantius refused to accept him as co-ruler. Magnentius then waged a civil war against Constantius, defeating him at the Battle of Mursa Major in 351. However, he was eventually defeated and killed by Constantius at the Battle of Mons Seleucus in 353.