Since the War of the Bend'r-mahk http://uesp.net/wiki/Shadowkey:Scroll_of_Shadow an http://uesp.net/wiki/Lore:Umbra%27_Keth#Umbra.27_Keth, a Shadow of Conflict, I wonder whether the Great War and the civil war in Skyrim, opposing the Empire and the Stormcloaks, created such creatures as well. Maybe the Forsworns' guerrilla created a minor Shadow of Conflict as well?

Do you think there is a link between Umbra and the entities called Umbra' Keths ?

I get the impression "Umbra" simply means "shadow"- perhaps in Aldmeris, perhaps in something else (if we're going real-world wise, Latin, obviously).

Keep in mind the creation of Umbra the sword/ Umbra the being: Clavicus Vile, in typical fashion, wanted a plaything that would send him souls. But when he tried to get a witch to create the sword for him, a piece of his soul was necessary to keep the weapon stable. This little piece somehow gained sentience and started calling itself "Umbra", functioning as a magical weapon with a life of its own, possessing its owners.

So perhaps the piece of Vile's soul just called itself "Shadow"- a reflection of power, even it if it wasn't as powerful as its source. Think about Peter Pan and his escaped shadow, which was less than enthusiastic about being sewn back onto its owner's feet. Similarly, Umbra the Shadow is in no rush to reunite with Vile.

i.e., no connection. Just a word.

The Dragonwar was an Umbra keth of the Ehlnofey war. The Civil war was an Umbra keth of the Dragonwar. The Forsworn were an Umbra keth of the Civil war.... unto the echo-need of hologram.

Alduin was in some ways the Umbra'Keth of the Civil War and Great War if anything.

When the sons of Skyrim spill their own blood...

Just speculating but maybe those wars spawned the power to give life back to Alduin if such things as Umbra'Keths are common.

This idea seems very interesting to me. Especially if one recall that in the http://www.uesp.net/wiki/Lore:Dragon_Alphabet, Alduin is described as an "ancient shadow unbound".

So what kind of conflict could have generated Alduin?

Furthermore, is Nirn itself a Shadow spawned by the conflict opposing Anu to Padomay?

I'd like to have the opinion of the lore buffs on this matter, cause I think this touches some very interesting and important feature of the Elder Scrolls world cosmology. (However, I am not competent enough to judge it.)

well according to lore from shadowkey shadows are not an absence of light but a reflection of mundus. kinda like another realm. If you look through the lore there are some creatures without shadows or refenceing certain times when a person has to fight his own shadow such as with the coc. It's part of a now almost forgotten magic dealing with that realm. As to the question on whether there was an umbra' keth. No there was not an umbra' keth because there was no shadowmage to raise it from the conflict.

I may be wrong, but I think the Umbra' Keth was spawned by the war, and then shadow mages tried to control it and strengthen it.

Umbra, penumbra and antumbra are simply names given to different parts of a shadow, mostly when referring to those cast by natural light.
I believe it is just a name chosen for its inherent 'cool-sounding-ness' and that all similarities with Vile are a coincidence.
Similarly compare, horizon, zenith, nadir, the latter two are often used as 'ominous' sounding names, or closer to Skyrim, cool sounding names from the bible such as Festus. (Or my own forum name.)

I may be wrong.

Ask thyself, Noble Pilgrim,

"What is the imperative of a fractal?"

I agree with Verbose. I'd like to see more inquiry around this. Along with Shadow magic (there was a thread on the subject a while back).

Though it seems we're about to delve into the duality debate all over again.