Loki Was Viking God and Embodiment of Fire?
If we think of the most complicated animal/monster figure in Norse mythology, what's likely to come into our mind is Fenrir the Wolf. If the most complicated god-like figure, it should be Loki. It is said that Loki was the god of fire in Norse mythology.
Short answer is: No, he wasn't.
Long answer is below.
We should kick off with Loki's family background. It is important to know that whether Loki was a Norse god or not remains a mystery. Surviving sources of Norse mythology can tell us that Loki's father was Farbauti "Cruel Striker" - a pure giant. But the identity of his mother is unknown. She could be Nal "Needle" or Laufey. No source can tell us whether Loki's mother was a goddess or a giantess or any form of being in Nine Worlds.
The common knowledge of Norse mythology is that Loki came from the land of the giant Jotunheim. He used his cunning mind and fast talk persuading the gods to allow him to live in Asgard the stronghold of Aesir gods. This somewhat suggests that Loki was a pure giant. Nonetheless, this remains to be seen.
Moreover, neither oral or written sources told us that the Vikings worshipped any god named Loki. By far, no cult of Loki has been found.
Secondly, it is weird that a god, if we consider Loki to be so, produced only monsters. Look at the children of Loki, none of them were in the ordinary form. Fenrir was a giant wolf with his jaws stretching from the earth to heaven. Jormungand was a giant serpent whose body encircled Midgard. And Hel though appearing as a woman looked more like a ghost. Sleipnir, another son of Loki, was an eight-legged horse whom Loki gifted to Odin. Loki also had two sons that were actually wolves.
Although some scholars do not agree with this point, it still suggests something abnormal about Loki.
The most notorious children of Loki: Jormungand the Midgard Serpent, Hel the Queen of Death, and Fenrir the Monstrous Wolf
Thirdly, it can be a misunderstanding between Loki and Logi. This misunderstanding originated in the tale that Thor and Loki visited Utgard-Loki in Jotunheim. During their visit, they met a giant king whose name was Utgard-Loki. The king held some contests for the gods and his servants. Loki joined the eating contest where he competed with the giant named Logi.
Loki lost the contest.
Later, Utgard-Loki explained that Logi was actually the embodiment of fire as his name indicated. In Old Norse, "Logi" means "fire" and who could win fire when it came to swallowing things. So, it might lead the readers to think that Logi was actually Logi.
But this doesn't seem right. Because Loki was famous for shapeshifting power, not duplicating power. In other words, while he could change his appearance into another form, he could not duplicate himself to compete with himself. Accordingly, it is more likely that Loki and Logi were two separate characters.
Overall, it is the safest to say the Loki was merely a Norse trickster. Because after all, we are yet to know whether Loki was the son of any giantess or not. And there has been no official evidence for us to conclude Loki was actually Logi in Utgard-Loki.