Above the gods stands something to which even Odin bows: fate. And fate has three shapes – the Norns, who sit at the foot of the world-tree and, in silent work, weave, fix and end the life of every being.
The Norns are the fate-women of Norse mythology. Three of them stand out: Urðr (that which has become), Verðandi (that which is becoming) and Skuld (that which shall be). They dwell at the Well of Urðr beneath the world-ash Yggdrasil and determine the fates of humans and gods alike.

The Völuspá describes how the three step from the lake beneath the tree and carve fate into wood. They „cast lots" and ordain life – not as mere fortune-tellers, but as the power that fixes past, present and future in the first place.
“Thence come the maidens / mighty in wisdom, / three from the dwelling / down ’neath the tree; / Urth is one named, / Verthandi the next, — / on the wood they scored, — / and Skuld the third. / Laws they made there, / and life allotted / to the sons of men, / and set their fates.”— Völuspá 20, translation after Henry Adams Bellows (public domain)
The Norns are also gardeners of the cosmos: each day they draw water from the well and pour it over Yggdrasil, along with white clay that guards the roots from rot. Without their care the world-tree – and with it the world – would wither. Fate here is no cold verdict, but tending and order.
The shattering thing about Norse thought: even the gods are subject to fate. Odin knows his end but cannot avert it – that is the heart of Ragnarök. The Norns embody this inescapable order; no power, no sacrifice, no cunning undoes it.

Beside the three great ones there are many lesser Norns who appear at every birth and set the newborn’s lot. Some descend from gods, some from elves, some from dwarves – and that, says the Edda, is why human fates turn out so differently: for one good, for another hard.
The Three Wells · Yggdrasil · Ragnarök · The Norse pantheon.
Völuspá, Fáfnismál, Grímnismál (Poetic Edda), English public domain: Henry Adams Bellows (1923). Snorri Sturluson, Gylfaginning. Scholarship: Rudolf Simek, Dictionary of Northern Mythology; Karen Bek-Pedersen, The Norns in Old Norse Mythology (2011).