It just figures that when Karkat finally finds that special someone he hates more than he hates himself, that person turns out to be the guy who's essentially his clone, but fifty million times more annoying.

Back at home, when he has time to examine it more closely, it quickly becomes obvious why this ritual never turned up in all his early research. It's not a typical soul summoning ritual. It's not a cultivation ritual at all; as Nie Huaisang puzzles through it, the closest category he can put it in is folk magic...not only that, but sex magic.