I thought it was pretty obvious that in the end, it was Atris who lured the Exile back to known space. It fits with her story, in that she became obsessed with finding these hidden Sith to save the Jedi, that she fell to the dark side herself and practically destroyed the Jedi. Luring out the Sith by leaking the location of the Jedi Conclave at Katarr proved she was capable and willing to do anything to lure out the Sith.
As for what she used to lure the Exile (i.e. why the Exile came back), is unknown, I guess. I vaguely remember someone asking the Exile why she returned to known space, at which point you get a few dialog lines to explain. I don't know who or where, though.