Odin hung himself on the world tree, Yggdrasil. He got initiated in the secret of the runes after sacrificing Himself to Himself for nine whole nights (Havamal). What higher sacrifice is there for a god to sacrifice himself (a god) to a god (himself)?
After the discovery of the runes, Odin experienced a rebirth. He became a much wiser god with the knowledge of the runes, which are, until this very day, used for magic and fortune-telling.
The image included in this post was a pyrography of my view on Yggdrasil. The roots could be the branches if you turn it upside-down. Odin is hanging upside down, making the ordeal extra hard. The piercing spear is also clearly visible.
According to some scolars, this image was used to start using the crucifixion story of jesus to convert the pagans in Europe, so that they could make the link between the Allfather and the 'saviour' of the catholic church, making it easier to let go of their original beliefs and ways of living. Before that time, the symbol of the christians was not the cross, but the fish... another example of the destructive nature of monotheism in ancient Europe....
Odin didn't stop after this sacrifice, his quest for wisdom only started....
At one of the roots of Yggdrasil is Mimir's well. Mimir (memory) drank for the well for wisdom. Odin became jealous and had to offer his eye to get the wisdom of Mimir.
This is quite symbolic: he sacrifices earthly vision for something much bigger.. As of that moment Odin required knowledge of past, present and future via his sacrificed eye in the well.
Later he also took Mimir's head.... but that's another story. His quest for wisdom was never satisfied, despite the fact that his fate was set: dying during Ragnarok.
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