Okay so let me start out with a few facts.
- If they refuse to go to the halls, their souls (their fea) can stick around
- It is more susceptible to corruption and shit, basically they lose who they are very quickly and just become this malicious wandering thing
- Sauron can gain control of them quite easily
- These wicked versions of the souls are noted as being put into bodies occasionally
- Originated from something (Tolkien couldn’t decide really) having to do with elves
- One version is that they’re tortured/corrupted elves
- One version is that they’re beasts/forms made by Melkor then animated like a “parrot”
- However they’re not just evil elves, their bodies are all fucked up too
- They reproduce in a human/animal/elf method, so their bodies are indeed biological
- If we’re going off Peter Jackson’s versions of them, not sure if this is also in the books, orcs can become immensely physically fucked up (head collapsed, head split in two, etc) and just generally a walking heap of deadly injuries and scars
So my concept for orc origin is that Melkor TRIED to make his own original beings, like elves or humans or dwarves, but couldn’t. He could only make Frankenstein’s monster-esque meat dolls. Sauron remedied this by taking the souls of dead elves, which once out of the body easily fall into an orc-like state in which they can speak, function, fight, etc but lose their old sense of self and take on a wickedness. Shove those fucked up souls into the meat dolls and there you go. Instead of making fresh meat dolls you can’t just reuse an actual corpse, which explains how and why orcs look so fucked up like mangled corpses.
I was sharing this in a discord chat with my friends a few days ago and there were some interesting takes/additions on this, like what if one of the bodies used or souls used was slightly recognizable to someone who knew them pre-orc.