Pope Leo VI (Leo the Philosopher) reigned for 7 months and 10 days during the second half of the 9th century; he died in 911. Little is known about him, but he is credited with the authorship of The Oracles of Leo the Wise, an illustrated 12th century Byzantine prophecy of future emperors, including the Last World Emperor:

"There will arise an imperial deliverer --- an oriental Frederick --- who will save the kingdom and the people. He will come from the Mohammedans over whom he will rule --- adorned with all virtue --- poor but needing nothing --- two angels in the form of eunuchs will accompany him --- mankind will accept him as their ruler. He will conquer the Arabs --- no taxes after 12 years. Immediately after, there will set in a period of darkness, crime and revolution."