Board Thread:Lore Discussion/@comment-26335203-20161005200021/@comment-173.29.210.71-20161028030750

Not the same guy, but hopefully this will help. Please disregard MNA as his answer is completely gamer-logic and not lore related at all. There is only a single universe in the Elder Scrolls series. This universe is known as Aurbis. Aurbis includes Mundus(the mortal plane where the world, Nirn, is located), Oblivion (home of the Daedra), the Void (cosmic emptiness like outer space, where Sithis rules and the Daedra originate), and Atherius (the Divine plane, with many smaller planes contained like Sovngarde. this is where the Aedra, like the Nine Divines, live. It is also believed to be where the souls of the dead go to, and surrounds the edges of Aurbis.)

Now, in the canon of the game series events, things often get complicated by things known as Dragon Breaks(named after Akatosh, the Dragon-God of Time). This happens when Time is rent into multiple possibilites. All of these timelines occur "simultaneously" withing Aurbis. After the Dragon Break resolves, all the timelines fuse and all have happened. This makes things often get very muddy as to the actual events that occured in the Break, because many of the possibilities will conflict with each other. It confuses Time and chronology to the point that entire days are lost without anyone recalling them, and some scholars in-lore even write the Dragon Break phenomenon off as a myth or cultural delusion.

The most well known Dragon Break, albeit probably the most minor one, is the Prison of Alduin at the peak of the Throat of the World. This is a good place to look at how it interferes locally with Mundus, as it was preformed in ancient times and persists to today, causing part of the peak to not actually fully exist in the material world. Another good example is The Warp in the West, with many wars and disasters happening in only 3 days, and the 2nd day being the most upheaving. With so much happening on the 2nd day in so many timelines, most couldn't recall the events at all. One thing that happened between Frostfall 9-11 is the conquering of northern Hammerfell by the armies of Sentinel. No one remembered the attack or invasion, they were just suddenly occupied and everyone other than the soldiers of Sentinel lost an entire day somehow, thinking the date was the day before. Another would be around the Illiac Bay. On the 9th of Frostfall, there were 44 independantly functioning states in the region. On the 11th, there were only 4. The leaders of the kingdoms recalled that a powerful weapon was discovered, and they had all attempted to get to it before any of the other one could. The next thing anyone knew, Wayrest had expanded to 4 times it's size and was being attacked by Sentinel, Orsinium, and Daggerfall. They didn't have time to even figure out what had happened, instead just mobilizing armies and the 4 powers were locked in a war. The 40 missing powers had all somehow been absorbed by the others, but no one knew how, and where the surviving kingdoms met, the land was scorched and barren.

So, there is only 1 Universe, Aurbis. There are, however, sometimes multiple timelines coexisiting in this universe, but they always converge and resolve, although usually fairly messily. This is different from an actual multiverse, where the timelines or "universes" don't have to interact or resolve with one another at all. The overall system is somewhat ill-defined, probably on purpose so as to not bind the lore-writers too tightly.