The Norns are at the base of the ash tree Yggdrasil (or, according to some versions, above the Bifröst bridge). They spin threads and weave the tapestry of fates. Each person's life is a thread in their loom. The length of the thread is the length of the person's life. Even the gods have their threads and are therefore not immortal, though the Norns hide the strings from the gods. So everything is set out beforehand. There is no luck, there is no randomness, everything is determined by destiny.