The book centers around several citizens of the fictional Iron Age Empire of Raumsdalia, a land whose inhabitants have Nordic names. Raumsdalia is situated south of a great steppe land which is bordered on the north by a vast, seemingly unending glacier.
When a gap opens in the glacier, Count Hamnet Thyssen and Ulric Skakki are dispatched by Emperor Sigvat II of Raumsdalia to explore the other side. Together with Earl Eyvind Torfinn and the wizard Audun Gilli, they team up with Trasamund, a chieftain of the nomadic, mammoth-herding Bizogot nation. Crossing through the gap, the explorers discover that a powerful tribal confederation, who call themselves "the Rulers," who have tamed woolly mammoths as battle mounts, are preparing to burst through the gap and seize the lands to the south for their own.