How Odin sacrificed his eye at Mimir's Well
As Odin sat on his high seat pondering the cosmos he was disturbed by certain whisperings among the branches of the great world tree Yggdrasil, the mighty tree that holds all the nine worlds in its high branches, from Asgard which is the kingdom of Odin and the Aesir, all the way down to Helheim, Hel's cold hall under the roots.
There, among the branches of the Old Tree, Odin listened to the rustlings of doom and of an uncertain future. But even with the wisdom he had gained from the runes he could not see far enough. He needed more clarity.
Odin knew of a great being named Mimir who lived among the roots of Yggdrasil and drank daily from a well of wisdom that he guarded day and night. The water bubbled up into this well from far under the roots. It reminded him of the well of Urd that held the runes that Odin had sacrificed himself for in older times.
Once again Allfather Odin decided to assume a disguise. His preferred disguise was that of an old man in a dark blue coat and floppy hat. A simple wanderer as not to attract unwanted attention and challenges. He didn't want to be bothered whilst on his great quest for wisdom, which was of the highest importance to Odin.
Allfather finally reached the roots in Jotunheim, the giant's realm, and there among the roots dwelt Mimir by his magical well.
Mimir heard Odin's approach, "Who approaches my abode!"
"It is I, Odin, chief of the Gods! I have come partake of your well of wisdom and knowledge," Odin said, suddenly revealing himself and calling out in a booming voice.
Mimir stood there by the well, an ancient being with flowing white hair. "Odin, whose gallows are Yggdrasil, you must know that there is a deep price to be asked for a draught from my well."
Odin approached the edge of the well and stared into its dark, rippling water. "Name your price and I will pay it," he said somberly.
"The price is one of your eyes Allfather. You must pluck out and drop it into the well so that all that stare into its waters will see the sacrifice of Odin" Mimir replied.
Odin took a deep breath and reached to his face, and with a grunt plucked out his right eye. In great pain he dropped his eye into the well of Mimir. There was then a shift in the breeze that seemed it to speak Odin's name and Yggdrasil's leaves rustled way up high.
Mimir took his horn Gjallarhorn and dipped it deep into the magical well and handed it to Odin, the now 'one eyed' god, and Odin drank deeply finishing it all in one draught.
That day Odin saw the future more than any god had ever seen before. Things that could be changed and those that could not. With only one eye he now saw better than he had ever before with two eyes. The insight he gained was far beyond description and he had more to ponder than he ever imagined.