Kind of droning doom fused with a bit of dubstep. Or dubstep fused with a bit of droning doom. Either way I refuse to coin the term doomstep. Because it's stupid.
The Pixie describes dubstep as sounding like giant robots having sex under water.
Necro Deathmort sound like that, except that it's happening at the bottom of the Mariana Trench, and the oceans are made of tar, and a planet is crashing into them in slow motion, and the planet is on fire.