Enderal: The Shards of Order is a mod for Skyrim currently being worked on that... how should I put this. Okay to give you a perspective of size, there is literally an option when you start a new file to either play Skyrim or play Enderal. It's a total conversion mod that basically takes Skyrim, and makes it's own world out of it.
There is literally no Tamriel in this setting, and apparently, Enderal has it's own lore, mythology, world (The world is called Vyn and it's the same world as Nehrim: At Fate's Edge, which some of you may have heard of if you've played Oblivion. There are also two other mods for Morrowind that take place in this world, Myar Aranath and Arktwend), races, soundtrack and is basically DayZ but for the TES series, or if in the far future, someone in Tamriel decides to make their version of the TES series then this would be it.