Do you mean the Immortals in the masks? The Immortals were the elite of Xerxes and named because their number never went under 10,000 because there were always people to replace them. I don't know what you're talking about, they don't fight any Vikings. Vikings were across the world, and they weren't really even prominent during the time of the war, I don't think...If so, a few had been conquered and annexed into Xerxes' side, because he had conquered quite a few nations according to the movie.