"CHIM is like lucid dreaming, but with superpowers." -Vivec
In the Elder Scrolls mythos, CHIM is the secret syllable of royalty. It refers to a state of sublime power in which one can alter reality itself to suit one's will. In our world, CHIM is basically the state that all writers aspire to.
Interestingly, CHIM comes with a bit of a downside: when a mortal being achieves CHIM, that being ceases to exist. As explained in the articles I managed to find on the subject while looking for the correct spelling of the word, use of this sublime power requires the following dual realization: self as dream, self as reality. They cancel one another out. In effect, the realization is a zero-sum.
That's what everyone calls it. So, Talos created Cyrodiil in its current form and ceased to exist. In so doing, he became the mythological forebear of the Empire, but he also became nothing. Honestly, calling it a downside may be inaccurate: if you never existed, you can't really suffer. In any case, it's not a downside for an author; it's just another part of the goal.
The last thing I'll say on CHIM is that, in fact, it is one of the concepts I draw on for my novel, Sacrifice.