10) "What are these auxilia buildings?"
The auxilia buildings slows down the game a bit by avoiding the "steam rolling affect" common in the vanilla game and reflects the fact that it took some time to change the culture of a settlement. The Phase I Auxilia structure represents your cultures subjegation of a foreign territory. The structure only gives you a population control benefit, but is necessary to construct the Phase II Auxilia structure. The Phase II structure, with some factions, allows you to recruit limited local troop types, and lends additional population control benefits. This is considered an abstraction of your colonization of the area. Finally, the Phase III Auxilia structure allows you to recruit all locally available native troop types, and also adds additional population control benefits. This structure is an abstraction that represents your cultures assimiliation of a native territory. You can only start to build your own faction's "core units" after you've finished building all of the auxilia buildings and completed the Provincial Barracks structure.
Additional Notes on Auxilia Barracks:
-The enemy military buildings are 100% useless to you.
-The military buildings work like this:
Auxilia Phase 1 = Gives a happiness bonus
Auxilia Phase 2 = Able to build basic AoR units in the area.
Auxilia Phase 3 = Able to build all AoR units in the area.
Barracks = Build basic faction units + all AoR units in the area.
Royal Barracks = All faction units + all AoR units in the area.