Midvinterblot was created by the same badasses that came up with Thor: the Norse. It literally means "mid-winter blood," and that sums up what it was all about. Humans were sacrificed around the solstice in an attempt to convince the gods to end the freezing Arctic winters. We... don't recommend celebrating this one too literally. Pictured: Carl Larsson's painting Midvinterblot, which depicts the sacrifice of Swedish king Domalde.