The Eddas know three different versions of the God Loki: Loki, Logi and Utgard-Loki. Whilst these are portrayed as three different personalities all three do overlap to a significant extent and demonstrate characteristics which may be derived from a single common source.
Frequently we find written that Wagner "incorrectly" portrayed Loki as a God of fire. Rudolf Simek in his Dictionary of Northern Mythology states:
"(Loge). A half-god created by R. Wagner in his opera Das Rheingold (tenor) who is the lord of fire. Loge probably is the result of Wagner`s confusion of the god Loki with the great Logi. In Snorri Logi is the personification of fire whereas the god Loki of Germanic mythology has nothing to do with fire."
I don`t accept that Wagner was "confused" about anything. He researched Germanic mythology thoroughly as part of his necessary preparation for his four part Der Ring des Nibelungen. It is clear that Wagner did conflate similar characters together-I do not deny this. After all this is a necessary device which film makers use when converting a novel to a screen play. However there is more to this than simple conflation.
I believe that Wagner realised that there was a link between Loki and Logi and he deliberately exploited this link to reunite a character or personality that had become split off into two separate individuals.
"Logi. (ON, `flame, fire`). A giant who is the impersonation of fire."
Logi appears in Gylfaginning in the tale of Utgard-Loki and the great magical contest waged by him against Thor, Loki and Thjalfi. He beats Loki in an eating contest because he is the personification of fire. However Loki doesn`t do a bad job of consuming the meal either!
Some scholars such as Wilhelm Waegner do see a link between Loki and the element of fire:
"At first Loki was held in high honour as the giver of warmth and god of the domestic hearth, and was looked upon as the brother of Odin and Honir, for the elements air, water and fire are intimately connected.
"The name Loki has been derived from the old word `liuhan`, to enlighten. It therefore has the same origin as the Latin lux, light. Thus he was also related to Lucifer (light-bringer), a title of honour which was given to the Prince of Darkness. In like manner as the northern tempter was chained to a sharp rock, Lucifer was believed in the middle ages to be chained down in hell. Saxo Grammaticus describes Utgarthlocus (Utgard-Loki) as laden with chains in Helheim, which proves that the myth of Loki and his punishment was believed long after the Christian era." [Asgard and the Gods].
This demonstrates a clear link not only between Loki and Loge but also between Loki and Utgard-Loki. The fact that Snorri portrays them as three separate entities does not disprove that originally they may very well have been one and the same person which over the process of time has split into three. This is not unheard of in mythology.
In the commentary to Saxo Grammaticus` The History of the Danes Books I-IX Dr Hilda Ellis Davidson states:
"In Snorri`s tale, Utgartha-Loki, whose name means the Loki of the Outer Regions (perhaps of foreign lands, or of the Other World) is represented by an enormous giant whom Thor and his comrades meet in the forest; he calls himself Skrymir, and it is some time before they realise that he is really Utgartha-Loki himself.
Saxo refers to a character called Gorm who sacrifices to Utgartha-Loki, indicating that He is indeed a God:
"Gorm solicited Utgartha-Loki with combined vows and propitiations and thus obtained the beneficial spell of weather they desired."
As mentioned above Utgard-Loki meets a similar fate to Loki:
"From here the visitors could see a murky, repulsive chamber, inside which they descried Utgartha-Loki, his hands and feet laden with a huge weight of fetters."
Further on in Saxo Utgard-Loki is specifically referred to as being a "god":
"He was unable to bear hearing this ugly and invidious report of Utgartha-Loki and was so grief-stricken about the god`s vile state that he gave up the ghost at the unendurable words , even while Thorkil was in the middle of his tale."
Loki and Utgard-Loki are both described as being Gods and both[like the other Gods] have giant heritage. The giants of Germanic mythology were, like the Titans of Classical mythology an earlier race of divine beings generically connected to the divine race that replaced them.
I contend therefore that if we are to learn more about Loki who is the Prometheus and Lucifer of the Teutonic world then we do need to research the characters of Logi and Utgard-Loki. Loki has quite rightly been compared to Prometheus and both meet the same punishment for betraying the other Gods. Prometheus is known for His gift of fire to men and Lucifer of course is a deity of light. The connections with Loki suggest an original common Aryan inheritance which would be of merit to explore further.
George W. Cox in The Mythology of the Aryans Nations, Volume II states:
"The name Loki, like that of the Latin Vulcanus, denotes the light or blaze of fire, and in such phrases as Locke dricker vand, Loki drinks water, described the phenomena of the sun drinking when its light streams in shafts from the cloud rifts to the earth or the waters beneath. The word thus carries us to the old verb liuhan, the Latin lucere, to shine, and to Logi as its earlier form, the modern German lohe, glow; but as the Greek tradition referred the name Oidipous......., to know and to swell, so a supposed connexion with the verb lukan, to shut or lock, substituted the name Loki for Logi, and modified his character accordingly."
In closing I feel that I have demonstrated quite clearly that Loki was indeed a deity of fire/light but I accept that at the same time like the other deities He is a multifaceted God.