Medieval mythographies, written in Latin, continue the conflation of Greek and Roman deities begun by the ancient Romans themselves. Perhaps because the name Pluto was used in both traditions, it appears widely in these Latin sources for the classical ruler of the underworld, who is also seen as the double, ally, or adjunct to the figure in Christian mythology known variously as the Devil, Satan, or Lucifer. The classical underworld deities became casually interchangeable with Satan as an embodiment of Hell. For instance, in the 9th century, Abbo Cernuus, the only witness whose account of the Siege of Paris survives, called the invading Vikings the "spawn of Pluto."