What is the Arcane Sprite reading? Smut? Fluff? Deity shipping?
All of the above, duh. The Arcanist is some hell of a deity.

His "diary" includes fan fictions, self-shipping, and a bit about his personal life. He (obviously) keeps it a secret from everyone else. I mean, who would want to read a smut fan fiction of the Lightweaver/Tidelord?

Probably the dirty sinner reading this. Have fun ;)