So this is related to the amounts of confusion of the second sun we saw in the C0DA preview, many people were wondering what this sun was? where did it come from? Did a race leave Mundus into Aetherius? Etc, etc.

After reading about the Middle Dawn it occurred to me, something so hidden yet fairly simple to understand. But first we must learn who Mnemoli is.

Mnemoli is a star orphan, one of the beings who became confused but delighted by the idea of the Aurbis and choose to stay but not give any parts of themselves in order to explore every part of this new creation that intrigues them. The Star Orphans primarily live in periods called "Un-time" a period of Un-time is a heavy unstable period where time can change at any moment the most notable example is the period of the first era called "The Middle Dawn" in which the Alessian Order Prophet Marukh broke Akatosh in order to remove Auriel which caused a Dragon Break that expanded from the 13th century to the 26th century of the first era.

Now what does Mnemoli have to do with moments of Un-time? Mnemoli is associated with un-time and during periods of Un-time her star glows the brightest. My theory is that the fifth era was such a great period of un-time that Mnemoli grew to become as large as the sun itself due to Numidium stomping around and being all teenage angst.