Orcs as Rising and Malignant Industrialization

 The wise sage-lords of the west devised clever contraptions that only require repetitive motion to do what skilled craftsmen could do, and much faster and of uniform quality. These manufactorums were soon filled with various commoners and riff-raff, but the constant toil bore great cost upon them, and much work was delayed. In addition, the fires that powered manufactorums issued forth inky smog that blotted out the sun. People couldn't work in these conditions, and they starved and broke down in droves. The wise sage-lords knew something had to be done, so they devised a solution.

Take a man and hammer the top of his head till it's flat, so exhaustion and tedium are incomprehensible for him. Screw metal into his spine so he doesn't need to sit. Inject oil into his joints so they never lock up. An orc is still a man, but they've been forcibly made a machine, they can still recall fleeting sensations and joys forever more lost to them, and they seethe with rage.

The sage-lords, in castles built to tower over the smog, will never notice their servitors' resentment, and with their knights, they believe they never will.