Deep, moody dubstep.  This is a dramatic piece which goes a lot of different directions, but was ultimately driven (as is the whole track) by the heavy bassline.

The electric piano was the last addition to the track, but has become the glue putting the whole thing together.

edit 03/14/19: Download Abyss from Bandcamp below, along with its previously mix-series-exclusive remix, in the new digital single.