Ayleids are thought to be descendants of the Aldmeri that came from Summerset Isles to Cyrodiil. They controlled the entire province of Cyrodiil until the Slave Rebellion of 1E 242 when the indigenous Cyrodillic and Nordic populations rebelled. The slaves successively overthrew the Ayleid rule and brought fourth the Age of Men on Tamriel. Thought the Ayleids were defeated their presence lingered in Cyrodiil for many hundreds of more years but they were never able to establish themselves as a political or military power again. The Ayleid's great fortress, White Gold Tower, became the Imperial Palace of today. Many of the Ayleids that remained were exiled, mostly to the province of Valenwood.
There are many theories that Ayleids are still alive today hiding out deep inside of fortresses and ruins, but the last sighting of one is over 1000 years old. Many doubt that Ayleids even made it to the Third Era.
There are more than 52 know Ayleid ruins in Cyrodiil, with an additional 35 Ayleid Wells found throughout Cyrodiil.
Much like the Dwemer, what little is known about the appearance of the Ayleid comes primarily from their architecture and early writings. Most Ayleid Ruins include at least one statue, presumably of an Ayleid warrior, usually holding a sword aloft. The general appearance looks similar to that of the Altmer, which most scholars consider fairly likely given the Altmer's concerted effort to maintain a "pure" Aldmeri appearance.