Across the past six or seven years, nobody in dance music seems as intimately connected with the doomsday end of the dubstep spectrum as Sam Shackleton. With seminal head-warping releases like "Death is Not Final," "Blood on My Hands," and "Stalker" stretching across his co-owned (and sadly defunct) Skull Disco imprint and labels like Perlon, Scuba's Hotflush and Mordant Music, Shackleton's become one of the form's most forward-thinking and consistent producers. Whether in a DJ set or booming from an apartment stereo, you recognize a Shackleton cut from those first murky moments: thick sub-bass pulses, African percussion that patters around the edges of samples that moan like a cold wind and subtly shifting melodic tones that creep underneath all the pounding. As Shackleton would be the first to admit though, his dour and often claustrophobic material is perhaps not the sort of stuff you'd typically associate with fabric's eminent mix series,...