I added Holger Danske to the the sidebar to the left. I like the story of Holger Danske. He was supposedly the son of the first king of Denmark, given as hostage to Charles Martel. Holger helped stem the tide at the Battle of Poiters in 732. He was featured in the Song of Roland, and later went on to headline his own epic poems. At the end of this life, he secluded himself deep underneath Kronborg castle at Helsingør (or “Elsinore”, per Shakespeare or Strange Brew).
He occupies the same archetypal space as King Arthur or the Emperor of Last Days (Frederick II was protrayed this way). He is a mythical figure who will return in the hour of greatest peril to save the kingdom when all hope is lost. Read about Holger here or here. One of my favorite books about the return of a mythical warrior is The Drawing of the Dark, by Tim Powers. It features King Arthur and beer, along with the Siege of Vienna in 1529.