I have heard I can unlock them but i dont know where to go or even what to do when i get there. I have beaten the game as the Bruiti, the Greek Cities, and I even conquered the entire map as the greek cities but I still havent unlocked all the factions.
Just copy and paste all the factions sans Slave under the "playable" section just like that. Make a copy of this file if you want and then save it. Now you should be able to play with all he factions, besides the Senate. You can't play with them. If the game screws up in any way after this, reinstall and try again. That's what I did. ;) --- Humanity's one redeeming virtue is the ability to corrupt anything.