Odin (Old Norse Odinn) is the chief of the Aesir, but he is not a god of straightforward strength; he is a god of knowledge, and the sources dwell on what he gives up to get it. To drink from the well of wisdom guarded by Mimir he surrenders an eye, and remains one-eyed thereafter. To win the runes he hangs nine nights on the world-tree Yggdrasil, wounded by a spear and given to himself, "myself to myself", the Havamal says, neither dead nor alive, until the runes are revealed to him. Knowledge, in these stories, always has a price, and Odin is the god who is willing to pay it.
He is also the god of poetry, of seidr (a form of sorcery), of the runes and of prophecy, and the god of the slain in battle. His hall is Valhalla, to which the valkyries carry chosen warriors, not as a reward so much as a mustering: they feast and fight there to be ready for the last battle.
A caution runs through his worship. Odin gives victory and inspiration but is famously faithless, taking his favourites to himself at the moment of triumph. The sagas treat him as a patron of kings and poets who is powerful, necessary and never quite to be trusted.