'Unlike my father,' said Thor fiercely, 'I believe in the seer's visions. He saw you entering the City of Ice.' 'Did he see me leave?' After barely surviving a giant mythical boar attack on her way to school, Cinder Moss realizes her questing days are far from over. Shield Maiden Trigga is back, newly promoted to Odin's Elite Guard and harbouring a secret too dark to share. Together, Cinder and the Valkyrie return to the Proving Grounds, hoping the Stormbringer can pick up where she left off, and save the Nine Realms from the Twilight of the Gods. As if the approach of Ragnarok wasn't bad enough, Thor's hammer has been taken for a murder he didn't commit. Or at least he claims he didn't do it. Cinder is not the only one that questions his innocence---the God of Thunder's closest allies in Asgard are dropping faster than the temperature in Jotunheim, and as Thor's Thronerunner, only Cinder can retrieve the legendary weapon from the City of Ice. No pressure. Can Cinder and her friends survive a horde of crocodile-human hybrids, a two-headed Elvis impersonator, a haunted hockey rink in Canada, and war with the frost giants? Thor has faith in Cinder, but Odin is betting against her. Again. The god's errand girl is back, and the ancient prophecy isn't going to fulfil itself.