Estalia doesn't really have much. Like... at all. It's the least-detailed nation in the Old World.
It's a patchwork of Spain-y towns and principalities with the largest being the city of Magritta. Not unified in any sense whatsoever. Invaded by Araby 1,000 years ago before knights from Bretonnia and the Empire helped drive them back and launch a crusade to Araby itself. Mymidia is as popular there as in Tilea. The Knights of Magritta are a secret society spread throughout Bretonnia, Tilea, and the Empire nominally based around uniting Estalia and launching another crusade against Araby (except they haven't really put any effort towards either goal and nobody actually sees any point in a crusade anymore). They're famous for their swordsmen known as Diestros.
There's really not much else.