The Academy's Immortal Professor [OP MC, LitRPG]

After a lifetime as humanity’s strongest, Lucian never expected to become a professor. Once he defeated the Demon Lord, Lucian disappeared to relax for a few centuries and only came back when an old friend called in a favor. Said friend also happened to be able to see the future, and apparently a whole string of disasters was on the way, all somehow tied to a certain academy. Naturally, Lucian was suspicious when the “solution” turned out to be him taking a teaching job there, but he was willing to give it a shot. All he had to deal with were scheming nobles, mysterious threats lurking beneath the surface, and a few old enemies who really should’ve stayed dead. Oh, and there was also a new, enigmatic System to worry about. Still, Lucian knew he could handle anything that came his way. Especially right after a good sandwich. New chapters are posted every Monday, Wednesday, and Friday.