Viking/Medieval Darcy/Steve, Jane/Thor AU based on this prompt ficlet.
After the death of their father, Lady Jane Foster and her illegitimate sister Darcy, who serves as her lady-in-waiting and occasional body guard, live alone quite happily in their castle in Lundenburh*. Until, that is, Vikings attack the castle, intent on burning it to the ground. While they’re rescuing what they can before everything burns, two strange men arrive, apparently there to save them, though they are quickly disabused of that notion. They are also Vikings, from Odin’s settlement in Ireland: Thor, his son, and Steven, the son of a Christian convert who curiously can’t grow any facial hair. Although Jane and Darcy don’t trust them, they go with them anyway to escape the sieges laying waste to Lundenburh, and return to Ireland with them, where they find out that, actually, it’s not so bad being a Viking.