This is one sinister and greatly done track. How long did this take anyways? Sounds like something I have heard from some movie trailers, kind of sad how they don't truly fit the movies though. This track is awesome though and I like how it feels it could double as a boss track of some kind and with it being a slow build up to the battle. Fun to see how you took one sound and made a whole track based around that sound.
The deep bass grinding sounds are pretty great to hear and I enjoyed that the most I think. The drums were simplistic and helped move the song along too. The synth has a slight machine sound to it at the start. Possibly the machine atmosphere sound from FL Studio? Then the rest of this song is just very awesome to hear. Excellent work.
Overall, amazing song as usual Rig!!