Yggdrasill or Ygdrasil
Literally, the horse of Yggr or Odin. In Norse mythology, the "Tree of the Universe," which sprang from the body of Ymir. It is an ash tree and has three roots. One extends to Niflheim with the well Hvergelmir where lies the dragon Nithhogg gnawing away its substance.
The second extends to Totunnheim and the well of Mimir, which is the source of all wisdom.
The third extends to Asgard. By it lies the well Urtharbrunn whose waters the Norns use to preserve Yggdrasill from decay. The squirrel Ratatosk runs up and down the trunk carrying strife. Four harts feed on Yggdrasill's foliage. An eagle and a hawk are sitting in its branches.