Complex sentence: Maximinus is described by several ancient sources (none of which, except for Herodian's "Roman History", was actually contemporary with Maximinus) as the first barbarian who wore the imperial purple and the first emperor never to set foot in Rome.
Split into simpler sentences: Maximinus is described by several ancient sources, though none are contemporary except Herodian's "Roman History". Maximinus was the first barbarian who wore the imperial purple and the first emperor never to set foot in Rome.