And I'll say more: Rose will fight The Fallen three times. Each time she will get a relic.
True Cross
Crown of Thorns
Holy Nail
No idea what the cross does for traversal, but the thorns will let her hang from pegs and the nail will let her pierce through floors.
About my other guess: The Fallen is Saint Louis.
He fought with a sword (sword on the card), he was king (ermine mantle), he became a saint (halo), and he had a "crown of thorns". If you notice, there are thorns scars in his arm, and his "whip" is thorn-like.