The Cult of Myrmidia is split. To the east, there are the Tileans. They believe Myrmidia was born in Remas, and was therefore a Tilean. Importantly, they believe that Myrmidia, as a Tilean, conquered Estalia. However, the Estalians to the west believe Myrmidia was born in Magritta, and was therefore an Estalian. Similarly, they believe Myrmidia, as an Estalian, conquered Tilea.
Both nations have their own versions of Myrmidia's holy texts to support their beliefs, and both are convinced they are correct. This fundamental difference has been the cause of, or the excuse for, much of the hostility between the Estalian kingdoms and the Tilean city-states down through the centuries. Indeed, the cult has almost broken in two over the issue on more than one occasion.
Currently, Magritta is considered to be the heart of the Myrmidian religion, although the high temple in Remas undermines this at every turn. La Aguila Ultima (or, as Tileans prefer, L'ultima Aquila), the Order of the Eagle's leader, is a Tilean woman; thus, the Tileans expected her to support Remas as the future centre of the cult. However, she controversially swore to accept the Estalian version of Myrmidia, and has moved to Magritta, where she is working hard to put this old division to rest.
This causes problems for the Empire branch of the Cult. The Order of the Eagle is sworn to obey a High Eagle from Tilea, thus they use the Tilean texts. However the templars receive their orders from Magritta, and, by default, accept the Estalian texts. To make matters a little more complex, the Eagle of the North has authority over the Order of the Righteous Spear in the Empire, and has been ordered to ensure the templars follow the Tilean texts, which, of course, they resist.
It is a massive divide, and one that, it seems, will inevitably tear the cult in two, which could plunge almost half of the Old World into an acrimonious and bitter war.