Odin

Odin was a deity in Norse mythology. He was the god of war, poetry and death, (PROSE: A History of Humankind) and was believed to be the king of the gods. (TV: The Girl Who Died) He was considered by historians to be one of the three most important Norse gods. (PROSE: A History of Humankind) His High German name was Wotan. (TV: The War Machines)

Biography
According to one of the Fourth Doctor's "time tales", Odin was in fact an actual deity. He elected to fulfil the term of the curse that the Viking captain Gundar called down on his mutinous crew, causing a storm which shipwrecked them on an unmarked island, and freezing them in time, such that they would remain there forever with no escape even in death. (COMIC: Dr. Who's Time Tales)

In another account, when the Third Doctor and Jo Grant met Odin in 141, they discovered that he was actually the human "High King" of all Sweden, who was mistakenly thought to be a god due to the power of Gungnir or Spear of Destiny, an alien artefact he possessed. He was the father of Thor, under the alias of Frey, influenced the Vanir, a tribe of Vikings in 141 to fight Odin, Thor and the Third Doctor so that he could get Gungnir. The Doctor explained to Jo at the time that Norse mythology probably came from real adventures of early Viking history, as here the fight between Vanir and Odin's folk. (PROSE: The Spear of Destiny)

Impersonations
When the Twelfth Doctor was captured by Vikings, he attempted to convince them he was Odin by using a yo-yo. Instead, they believed the leader of the Mire, who appeared to them from the sky and used a "very realistic hologram" to project the appearance of a bearded, one-eyed man, was the real Odin. (TV: The Girl Who Died)