Ryse: Son of Rome has a free update that adds two new levels events in the multiplayer gladiator arenas.
Killing barbarians will now trigger random events to occur across the maps, such as a turret popping up and lobbing arrows at you until you destroy it.
In the other new event, Reward Statues of Roman deities will rise from the sands and toss one-time buff bonuses to your health or focus meters.
Of course there is a new map pack as well if you'd prefer that sort of thing. The Colosseum Pack adds two arenas—an ancient forest shrine and Hades' lair (which again, is the GREEK name for the god and not the Roman)—and two new skins. The pack costs $3.99.