In Age of Alexander, you can add a new army group (like greek group, persian group, barbarian group, carthage group and roman group) by incorporating the federated partner's technology into your technology tree: for example, Sparta can acquire the barbarian army group by federating with the Illyrian barbarians. But this is the only DLC where this works... In Rome vs Carthage, it doesn't work at all, despite the announcements on the screen. Sparta doesn't get any of the barbarian technology back and stays ...

?

I looked them up in the Imperiums Library, but it didn't tell me where they originate. Where can you create them?

Is there a quick way to see which cities can build which units?

I keep getting as an achievement various groups that I am neither playing nor have defeated. It seems completely random so I doubt that this is the intended behavior.