Pope Leo IV was the Pope and head of Christianity when the young Alfred visited Rome on a pilgrimage.
The Pope granted an audience to Aethelwulf, Alfred and Prudentius when they visited Rome on a pilgrimage, sent there by King Ecbert. When they arrived, the Pope showed one of the greatest treasures they had in Rome to Alfred, a thorn from the crown that was put on the head of Jesus Christ before the crucifixion. Later, he gifted Alfred with a sword, so that he could cast out all his enemies. He then crowned Alfred a consul of Rome, just like Caesar, preparing him for whichever future God prepared for him. During the cerimony, Leo IV revealed to Alfred that he saw a young monk walking beside the boy, who then vanished. (Death All 'Round)
- Leo IV was portrayed by John Kavanagh, the same actor who portrays the The Seer, a curious nod to the opposite and yet similar positions of authority in their respective religions.
- The real Leo IV was Bishop of Rome from 847 to 855.
|Season four appearances|
|A Good Treason||Kill the Queen||Mercy||Yol||Promised|
|What Might Have Been||The Profit and the Loss||Portage||Death All 'Round||The Last Ship|
|The Outsider||The Vision||Two Journeys||In the Uncertain Hour Before the Morning||All His Angels|
|Crossings||The Great Army||Revenge||On the Eve||The Reckoning|