While not strictly hip-hop, Amon Tobin is definitely dark, but in a curiously playful kind of way. He's definitely imbibed his fair share of hip-hop influences, though he also seems to have imbibed influences of Brazilia, drum n' bass, classical, industrial, jazz and god knows what else. But his resulting work always transcends definition -- it's as if Tobin had never heard any music except that which was in his head. Even more wonderfully, he passes this experience of hearing music for the first time on to you. And yes, it's all instrumental.
Given your tastes, I would first check out his 2002 single "Verbal" and explore from there. Enjoy!