You truly feel like the last emperor of a dying civilisation. Overstretched, undermanned and threatened on all sides by migrating tribes and upstart kingdoms, playing as Rome is a panic from turn one. The opposite of the Nomadic tribes, but no less challenging, are the decaying Western and Eastern Roman empires.
Your people are now starving, but at least you have some walls to hide behind. Nomads can occupy a city and claim it as their new homeland, turning them into a more traditional faction but creating a whole new problem those mobile farms you've spent ages building? They're gone. Fortified cities, or large armies approaching, genuinely makes you afraid - your people are vulnerable, landless and alone and boy, do you feel it. Playing as a nomadic tribe is a balancing act between moving, raiding and camping. In lieu of a city, these forces must encamp to raise money, gather food and create units.
Set during an age where the Huns and worsening climate drove nations from their homes and turned them nomadic, the game has factions who start without a home (Alans, Goths and Huns).