The Huns as a faction will be familiar to any players of Rome: Total War: Barbarian Invasion, Attila also includes an improved and reworked version of the horde mechanics from that game. Attila is not yet in power at the start of the game, but will later be able to become the leader of the Huns.
Total War: Attila is set in the late Roman period starting in 395 AD, during the period now called Late Antiquity. 2.5.6 The Age Of Charlemagne Campaign Pack.