Interpretation (SPOILERS)
The silent One-Eye is the incarnation of Odin. He is invincible and holds the power to see the future. He disdains the Christian Vikings who've usurped his influence over his people. He tests many in battle to see if they're worthy, but finds none. Nevertheless, he sullenly sees his people off to their new (holy) land, America, where Scandinavians were the third most numerous immigrants. The Boy is a type of Thor, Odin's son (note his hammer necklace), who will sort of replace him in America once the grim god ironically sacrifices himself à la Jesus Christ.
(Yes, I realize there's another thread on this topic, but I thought the main ideas could be conveyed more succinctly with my spin on them).