A

A or Aeh was the original Void, where it stayed until it learned it's brother Yu existed. A is the first deity and embodiment of the Void, until A split itself from the Void to create The Firstborn.

A's Departure
Once A decided to leave the Void, thus splitting it, A and Yu were destroyed. However, as A was the cause of the split, when Yu was destroyed it managed to throw itself into the planet Centrum, creating the Glass of All, a powerful artifact that could see the future.

The Great Failure
As A's intent was that splitting the Void would kill Yu, thus rendering the impossibility that what will happen could be known to disappear. This was however a failure in A's part, as Yu knowing what will happen meant it knew A would split from the Void, thus Yu threw itself into Aduwey to render A's attempt useless.