Old Yggdrasil conceals many secrets, not least of all the location where may be found The Norns.
Dare to travel the tree for as many lifetimes as you care to supply, and you may never happen upon their pool.
Or, should they wish it so, you may never escape their pool.
The squirrel Ratatoskr is one of the rare beings able to travel the Tree at will. But even he has trouble finding the Norns unless they wish it. And they rarely do, unless they require his services to whisper gossip they wish released into the worlds.
All that I say is true, for I heard it of Ratatoskr himself.