I know Czernobog, the Slavic god of darkness, mainly from Neil Gaiman's novel "American Gods". There is a scene in which Czernobog, Anansi (African spider god and trickster) and Shadow (the son of the Norse god Odin) each move into a motel room. Czernobog gets number seven, Anansi number eight, and Shadow number nine.
As for the other two, I understand the allusions - a spider has eight legs, and Odin hung on the Yggdrasil tree for nine days and nights. But what about Czernobog and the Seven?
