Naming of moons underworld, and Nix (a respelling of Nyx), mother of Charon, is the goddess of darkness and the night. Kerberos is a giant three-headed dog who guards the entrance to the underworld. The fifth moon is named for the river Styx that forms the boundary between the worlds of the living and the dead. The name of Eris's moon Dysnomia was suggested by its discoverer Michael E. Brown, who also suggested the name of the dwarf planet. The name has two meanings: in mythology Dysnomia (lawlessness) is the daughter of Eris (chaos). However, the name is also an intentional reference to
Underworld: Rise of the Lycans Lakeshore planned to release a prequel as the third film following "Underworld"s sequel, "" (2006). Kate Beckinsale, who portrayed Selene in "Underworld", expressed interest in reprising her role for the sequel and the prequel. In December 2005, "Underworld: Evolution" director Len Wiseman explained that the "Underworld" franchise was originally conceived as a trilogy. Wiseman said, "We sort of mapped out an entire history and story... a massive collection of ideas and stories that we're putting out at certain times." Wiseman anticipated creating a third installment for the franchise based on the audience's reception of "Underworld: Evolution", which would be released