Stories begin when characters set out on their travels and end when they arrive at a destination or return wearily home, but what matters to the storyteller is the middle of the journey with its middle-aged complexities -- divided loyalties, tormenting decisions about which way to turn. Myths are simpler, starker and more abrupt. They ignore the median region and its middling conflicts; their province is a beginning we can't remember and an end we may not be alive to experience. How did the world originate, and who, if anyone, made it? And how will its conclusion come about -- a firestorm or a blizzard, inundation by black waters, or an angry deity's brusque decision to stop the show? When AS Byatt agreed to contribute to Canongate's series of updated myths, she chose as her subject the ultimate end, the Scandinavian legend of Ragnarok . This is what Richard Wagner , in the last instalment of his Ring cycle , called the twilight of the gods, who give up regulating nature and allow the world to destroy itself. Because apocalypse overwhelms individual fates, Byatt could hardly follow the example of previous writers in the series, who have extracted characters from the myths and probed their minds: Margaret Atwood in The Penelopiad asks why Odysseus slew his wife Penelope's maids, while David Grossman in Lion's Honey investigates the motives of the temple-toppling Samson, whom he likens to a contemporary suicide bomber. Byatt chose to deal with elemental forces, personifications of the