Mythology
(Remember, this is strictly for background as the only place that is played out in our settings is The Legend of Last Gate)
The Uncharted Midlands Persistent World uses an original mythology simply called "The Midlands", specifically made for this concept. It is a low-magic fantasy settings, based on a mix of D&D and Tolkein, which everyone can help develop and improve if you feel details are insufficient or want to add layers of interest and complexity. Please use the mythology forum for that. Mythology information:
(Playable) Races and Geography of the Midlands
Magic, The Aether, and Wizards
Last Gate Introduction (important for new players)