Go ahead and start whenever you are ready. What century makes sense for the first rise of Asmodeus? I pulled the 8th century out of a hat and figured I'd change it later.
bro i will need help then because i'm introducing tale as a "person that garnet vaguely recognizes but can't really because she mothers too many people".
I tell the neophyte: Write a million words–the absolute best you can write, then throw it all away and bravely turn your back on what you have written. At that point, you’re ready to begin. — David Eddings