As the explosive second half of Season 5 begins, Ivar the Boneless' tyrannical reign as king of Kattegat ushers in a new Dark Age for Scandinavia. And while Bjorn and Lagertha flee Ivar's murderous forces with Bishop Heahmund, Duke Rollo's return brings even more upheaval. Meanwhile, Floki battles the elements – as well as his settlers' lust for revenge – in beautiful, desolate Iceland. Ultimately, the sons of Ragnar and old sworn enemies must become allies to challenge the despot Ivar, who has declared himself a god. The gut-wrenching action and dramatic plot twists reach a fever pitch as the season unfolds.