Possible Clues:

• Catholic university near Tampa, Fla
• Pope who negotiated with Attila the Hun
• Fifth cen. pope
• Fifth-cen. pope called 'The Great'
• Designation for five popes
• Fifth cen. pope called 'The Great'
• Designation of five popes
• Tampa suburb named after a pope
• Canonized pope of the fifth century
• Pope who convinced Attila to turn back his invasion of Italy