The highest and the oldest of all the gods is Odin.

Odin knows many secrets. He gave an eye for wisdom. More than that,
for knowledge of runes, and for power, he sacrificed himself to himself.
He hung from the world-tree, Yggdrasil, hung there for nine nights. His
side was pierced by the point of a spear, which wounded him gravely. The
winds clutched at him, buffeted his body as it hung. Nothing did he eat for
nine days or nine nights, nothing did he drink. He was alone there, in pain,
the light of his life slowly going out.
He was cold, in agony, and on the point of death when his sacrifice bore
dark fruit: in the ecstasy of his agony he looked down, and the runes were
revealed to him. He knew them, and understood them and their power. The
rope broke then, and he fell, screaming, from the tree.
Now he understood magic. Now the world was his to control.
Odin has many names. He is the all-father, the lord of the slain, the
gallows god. He is the god of cargoes and of prisoners. He is called Grimnir
and Third. He has different names in every country (for he is worshipped in
different forms and in many tongues, but it is always Odin they worship).
He travels from place to place in disguise, to see the world as people see
it. When he walks among us, he does so as a tall man, wearing a cloak and
hat.

He has two ravens, whom he calls Huginn and Muninn, which mean
“thought” and “memory.” These birds fly back and forth across the world,
seeking news and bringing Odin all the knowledge of things. They perch on
his shoulders and whisper into his ears.
When he sits on his high throne at Hlidskjalf, he observes all things,
wherever they may be. Nothing can be hidden from him.
He brought war into the world: battles are begun by throwing a spear at
the hostile army, dedicating the battle and its deaths to Odin. If you survive in
battle, it is with Odin’s grace, and if you fall it is because he has betrayed
you.

If you fall bravely in war the Valkyries, beautiful battle-maidens who
collect the souls of the noble dead, will take you and bring you to the hall
known as Valhalla. He will be waiting for you in Valhalla, and there you will
drink and fight and feast and battle, with Odin as your leader.