Ancient Wizard, Founder of the Oswyn College, Long Missing
Benedict Oswyn founded the Oswyn College of Thraumaturgy after years of traveling the planes in search of perfect knowledge. His endowment to the school was a set of magical items containing pieces of his own soul, so that he could forever guide the school. Such items are not made without great cost, and the day after the last item was presented to the new Dean Oswyn disappeared, his fate unknown.
The only thing Oswyn left behind was careful instructions on how to maintain these relics. Every century the entire set must be taken to the Eternal Spring, located somewhere in the astral sea, and dipped in the restoring waters that flow there. Oswyn was not foolish enough to just provide the location of such a powerful magical locale, instead he left a single instruction for those that would bear the relics: “go to Sigil, the City of Doors, and take the relics to the great library.”