After the creation of the universe, the elder gods grew weary and desired to rest for a few millennia. They wished to appoint Odin as the guardian of Asgard and make him the Allfather. But they would not be satisfied with the appointment until the fledgling god had proven himself. They told him that he would inherit their kingdom in the branches of the great world tree only if he could delve its roots and learn the lessons of the waters of the three pools they had placed there when the tree was first formed.
Odin, who had - as yet - never known fear, donned his robe of midnight blue and took up his sword and strode boldly down the rainbow bridge, across Midgard, past the bridge of the dead, and finally into the lowest parts of the world tree. The first pool he encountered was dark with mud, and several great roots filled much of it. The roots constantly bled into the muddy water, leaving a wake as black as oil.
But Odin wasn’t afraid. He waded into the muddy morass until the water had closed over his head. He grabbed onto the roots of the tree and held them tightly, even though they were covered with prickers like arrowheads that burned his hands like fire. But Odin wasn’t daunted. For nine days and nights he held both his breath and the painful roots. And insight came to him on the last day, prompting him to take one hand from the roots and grab his sword. This he used to create eight wooden blocks from the tree and carve runic symbols upon them. These he read before deciding to carve eight more. Then, finally, he knew the runes would be complete when he had carved a third set of eight. After this was done, he let go of the stinging roots and floated back up to the surface. He was now master of the runes; he had taken the first step toward becoming the keeper of Asgard.
The second pool Odin encountered was clear, though it was very small. In fact, it was only a little bigger than a puddle - but its waters were those which dripped from the roots of plants placed by the wisest of the elves in the kingdoms above. A silver chalice - full of the water of the pool - sat on a small white table; but Odin, reaching for it, could not bring it to his hand. Wherever he thought he saw the vessel, the place was empty when he put his hands there. The chalice was always just a little to the left, the right, above or below his grasp. His head began to grow as weary as his limbs as he struggled to obtain the cup.
But Odin knew that he could drink from the vessel. If his body failed him, then his mind would help him figure out a solution. He decided to consult the runes he had so recently carved. He asked them how he might bring the chalice into his hand, and they gave him an answer. Odin closed one of his eyes and, in his altered vision, detected the true position of the cup. He hefted it to his thirsty lips and drank the water from it. Now his eyes could see all sorts of things, even things that happened many miles away in different realms of the world tree. He also spied the secret path to the third pool and made his way toward it.
The third pool was wide, and its waters churned constantly about. Odin stopped before he could reach its edge, however, for his new eyesight told him that there was already someone there: an old woman, her hair steel gray and her eyes as cold as stars at midnight. Gazing upon her, Odin experienced fear for the first time in his life. When he looked down, he found that he was naked. When he looked up again, he beheld a terrible sight: the washer woman was removing copious bloodstains from the garment she held. A wake of red flowed away from her hands, which held a robe of deepest blue. His robe. His blood.
Odin shrank away, pulling into himself. But no. He would not let his fear rule him. He fought hard against the paralyzing terror until he could stand again, until he could once again behold the bloody vision before him.
Then Odin learned the third lesson of the pools, and it was this that finally entitled him to the keys of Asgard. He comprehended that, in spite of his power and his intelligence and his courage, he was helpless against this woman - a woman who could change the very rules of time. He was afraid, and there was nothing he could do but wait and hope. And so he chose not to act. He simply awaited the decision of a force that made his very existence insubstantial. He waited in silence as the washer woman strolled toward him, touched him softly with her sharp fingernails and placed the bloody garment about his body. Odin finally fainted with fear, but he didn’t resist.
When the god awoke, he found himself in the kingdom of Asgard, among the highest branches of the tree of worlds. He clutched his sword in one hand, while the other held the runes. He took these and moved forward, for he could see his new keep on the horizon.