Also if you go into the game's settlements.xml files you will find the names of other tribes such as the Dryatics, Ialoi, Vakken, Vanni, and Laconians. Of course the games encyclopedia entries are not perfectly accurate, but there are a lot of interest lore nuggets you could use. Like the entry for Myzea said a senator named Lito once tried to set up an independent "barbarian republic" of the Palaic people in the area.
Some of the entries also give you the ancient names of settlement such as Charas being Charasea or Rhotae being Rotash.
Fun fact, the entries say that Charas was the first capital of the Empire and thought to the first settlement of Caladrios the Great.