The main enemy of YHTBTR (and the only other character present) is called the Grinning Colossus. It is a giant, pitch-black mass with only a mouth and bulging eyes that can't be killed by your weapons. In any other context, it would make a good monster in a typical creepypasta. If you look at its expression closely, it doesn't look like the Grinning Colossus is grinning at all, but rather like it's constantly screaming out in agony (driving home the torture theme). You can try to kill it with your weapons, but even if you do somehow manage to get it down to 0 health it still survives (which can be done via a hack seen here: http://www.youtube.com/watch?v=fA7UqQtUS7g
), which is another Sisyphean torture in itself.
Another possible interpretation of the Grinning Colossus' appearance can be representative of the victim of a lynching. Billie Holiday's infamous Strange Fruit, a song about lynching African Americans in the South, includes these lines:
"Black bodies swinging in the Southern breeze / Strange fruit hanging from the poplar trees / Pastoral scene of the gallant South / The bulging eyes and the twisted mouth" (http://www.billieholidaysongs.com/lyrics_strange_fruit.htm
I'd rather not include a picture, so this description will have to do.
When looking at the Grinning Colossus, you can see these characteristics (black body, bulging eyes, twisted mouth in agony) showing through almost exactly as they are described. This is especially so in the Grinning Colossus' death animation. [see picture] The fact that lynching is another kind of torture involving a rope should be noted as well.