Yggdrasil Picture

In Norse Mythology, the axis of the universe was an enormous ash tree, Yggdrasil, also known as the World Tree, which formed a column linking the worlds of the gods, the giants, and the dead. It's fortunes mirrored those of the universe it sheltered; as well as sustaining the world, it suffered in the same way as those who lived in it.
A variety of creatures dwelled in or by the tree:
A wise eagle who sat in it's uppermost branches, with a hawk called Vedrfolnir between it's eyes; a monstrous serpent, Nidhogg, who lay deep down in Nilfheim, by it's roots; a squirrel named Ratatosk who ran up and down its trunk carrying insults between the eagle and the serpent; and four stags, named Dain, Dvalin, Duneyr and Durathror, who lived among the tree's branches eating young shoots.
To them and others the tree was a source of life.
Hel
The giant Adamastor
Yggdrasil
Earth Shatterer
Lernaean Hydra