Yggdrasil in Norse mythology is an ash tree that supports the universe:"A wonderous ash-tree, YGGDRASIL, supported the universe. It struck its roots through the worlds. Three roots there are to Yggdrasil. Hel lives beneath the first. Beneath the second the frost giants, and men beneath the third." It is also said that "one of the roots goes up to Asgard." Beside this root was a well of white water, URDA'S WELL, so holy that none might drink of it. The three NORNS guarded it, who allot their lives to the sons of men, and assign them to their fate. The three were URDA(the past), VERDANDI(the present), and SKULD(the future). Here each day the gods came, passing over the quivering rainbow bridge to sit beside the well and pass judgement on the deeds of men. Another well beneath the root was THE WELL OF KNOWLEDGE, guarded by MIMIR THE WISE. Over Yggdrasil, as over Asgard, hung the threat of destruction. Like the gods, it too was doomed to die. A serpent and his brood gnawed continuously at the root beside Niflheim, Hel's home. Someday they will succeed in killing the tree, and the universe will come crashing down.