Magnentius in Harpers Dictionary of Classical Antiquities

A German by birth who conspired against the life of the emperor Constans, whom he caused to be murdered in his bed. Subsequently, being pursued by the vengeance of Constantius, and defeated by him at the battle of Mursa (a. d. 351), he took his own life by falling on his sword. His reign lasted from A.D. 350 to 353. His full name was Flavius Popilius Magnentius. See Victor, Caes. 41 and 42.