I was doing a completely unrelated search on TIL, and I found not one, but two references to Homunculi.

The first, A Hypothetical Treachery:



These Homunculi are apparently some of the inhabitants of Eldengrove, an area of Valenwood.

The next reference comes from none other that the Thirty-Six Lessons of Vivec: Sermon One:



After a bit more searching, I found that there is a creature in TES I: Arena known as a Homunculus. From the UESPWiki:



It would seem that these Homunculi do exist in the ES universe. However, these are the only references to said creatures that I could find. Is there any other official lore on them that I may have missed?

It seems like you've done a great deal of searching. There probably isn't. At least not any more official pieces, outside of stuff that may be on the forums.

No lore that I am aware of. Congratulations, you can now make up stuff! Rare finds like these should be treasured, for they nothing to go by, other than they exist.

Homoculus are enemies from Arena. They're similar to demons.

http://www.uesp.net/wiki/Arena:Monsters#Homonculus

But since it's from Arena, it may not hold true in the current lore.

Now the other references listed may be true, but they really don't seem to tell us much except giving the name "homunculi", it doesn't tell us anything about the properties of them or anything else, so I suppose it's fertilizer for our epileptic trees.

They weren't called Homunculi, but up until the events of Oblivion it was strongly implied that Uriel's sons were some type of doppelgangers planted by Jagar Tharn during his reign as the false Emperor, the real ones either being killed or imprisoned.

A false heir isn't quite the same thing as an artificial construct.

Daggerfall & Oblivion replaced the homunculi with imps.

Maybe, but they're not the same thing.

Of course not. Homoculi are dangerous, powerful, creatures made by insane wizards who need some extra muscle. Imps are pansy little flappy creatures who just happen to look similar.

Additionally, Tharn was explicitly stated to be a master of Illusion. It's likely that if he did it, he'd have just charmed up some lackeys to the point where they could pass most tests.

I've also done some research on Homunculi in the TES universe, but I could only find the things that you already mentioned

The name actually DOES tell us a bit about their properties.
"Homo" is the Latin name for man and "©ulus" is the Latin diminutive. However, I believe the correct Latin term for little man would be "hominculus", though even then it's clear that Beth referred to the Latin word. The remark of the plural being "homunculi" also clearly showcases the Latin origin.

It feels like having a negative side tone, so it suggests these homonculi are little/worthless sidekicks with human characteristics. See them as the evil little twins of Cherubs.

How do Homunculi come out of Seht's hand "like rope" then?

It's the Sermons. I mean...dude, it's the Sermons.