It includes "four fully-animated units" with the Roman Aquilifer and the Gallic Hornblower among them. They integrate into veteran units for a small morale boost. It's a 'thank you' from the devs.
Longbow aren't suddenly wrapping up support though, in case you thought this a farewell gift. The studio promise 'larger content' is on the march for the strategy game.
"The free Bannermen DLC for Hegemony Rome: The Rise of Caesar adds four new and fully-animated units to the game: including the Roman Aquilifer and the Gallic Hornblower. These will be automatically added to your AI units upon download and will be placed in proportion to the ranks and upgrades of your associated officers - as well as making your veteran units look more distinctive and impressive on the battlefield."
The Bannermen Pack is available to view throughand is entirely free.