There stands an ash called Yggdrasil,
A mighty tree showered in white hail.
From there come the dews that fall in the valleys.
It stands evergreen above Urd’s Well.
From there come maidens, very wise,
Three from the lake that stands beneath the pole.
One is called Urd, another Verdandi,
Skuld the third; they carve into the tree
The lives and destinies of children.
The World Tree is inhabited by several animals, the Nidhogg, pet dragon of the goddess Hel which chews the roots of the tree which bind it, Vidopnir the rooster, who will crow when Ragnarok occurs, Ratatosk the squirrel, who carries messages of hate between the eagle and the Nidhogg. This eagle, who is not named, is said to have knowledge of many things, and on its head sits Vedrfolnir the hawk. Four deer, Dain, Dvalin, Duneyr, and Dyrathror, nibble the highest shoots.
The residents of the Well of Urd, the Norns, design the earliest form of the destinies of all of the beings who live in the Nine Worlds of Yggdrasil, from humans to slugs to gods to giants.
All beings who are subject to destiny have some degree of agency in shaping their own destiny and the destinies of others—this is the dew that falls back into the well from the branches of the tree, accordingly reshaping the past and its influence upon the present. All beings do this passively; those who practice magic do it actively.
The practice of magic is viewed as being precisely the process of gaining a greater degree of control over destiny. There is no absolutely free will, just as there is no absolutely unalterable fate; instead, life is lived somewhere between these two extremes. We are all created creators, carrying forward the world’s ceaseless reinvention of itself.