Both are Roman-themed military organizations that favor melee weaponry. Both are ruled by an emporer who claims to be of divine lineage. Both are obsessed with expanding their borders through any means necessary. The Imperial Legion obviously has superior armor and bladed weapons at their command, while Caesar's Legion uses pieced-together armor collected from fallen foes. However, they're known to occasionally pull out guns. The Imperial Legion upholds a more or less stable, hands-off government, while Caesar's Legion is fascist and totalitarian (though, the Imperials could be argued to be the same).
So, if both sides were to meet on the field of battle, who would emerge victorious?
