well i have played jk 2 and jka but there is something i dont get, after Vader and the Empror are dead then all the siths are dead, and luke brings balance to the force, so howe is it that desan and tavon goes over to the dark side when there are no siths?
Jedi don't need a Sith in order to turn to the Dark Side. A Dark Jedi is just a Jedi who utilises the Dark Side and lives by it's principles. Try the WikiPedia entries for "Dark Jedi" and "Sith", those will explain a lot better than I ever could.
I don't know how, and I don't know why, but this is totally Sheep's fault.
As long as a Jedi has "dark" feelings (anger, greed, etc) it will eventually turn to the dark side of the force.
*slaps forehead* http://en.wikipedia.org/wiki/Main_Page