The book, it came after children of dune
https://bookwyrm.social/book/161586/s/god-emperor-of-dune-dune-chronicles-4
That it doesn't matter how powerful wizard you are, you'll still need to find a way to pay your rent.
I learned about him fairly recently too. The end of his life struck me as brutal.
I mean how everyone began to treat him in the absence of the emperor. I don't know, maybe I'm just used to Japan being an innately ethnically warm culture.