Pope Leo I is based on an Italian aristocrat and pope with the same name who is also known as Saint Leo the Great. In Age of Empires II: The Conquerors, he is featured in The Fall of Rome in the Attila the Hun campaign, where he appears at the end and talks to Attila privately in order to convince him to abandon his invasion of Italy. He is also available in the Scenario Editor.

In-game, he has the appearance of a Monk. Like other Monks, Pope Leo I is affected by all upgrades that affect Monks, as well as any other bonuses that affect them. As a hero, he cannot be converted and can regenerate health. If he picks up a Relic, an unresolved glitch turns him into a regular Monk.

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