Other translations call it the "path of the warlock" which makes it make alot more sense.
It means whatever he is planning on will involve him embracing Geass fully, and venturing into unknown territory. Some have theorized that it will entail him becoming immortal and then attaining some new level of Geass-related power after that, but nobody knows for sure.
It wouldn't be far fetched to link this "path of the warlock" stuff to what he does to Kallen. Spoilers say he will lie to her to drive her away, but Kallen will realize that he was just trying to protect her and follow him anyway. It stands to reason that the reason Lelouch would do such a thing would mean that he believes that the "path of the warlock" will destroy everyone around him.
It seems as though the show is setting up for Lelouch to be surrounded by a few core elites and between them and a massive powerup for himself, he will somehow come out of this with a win.