In the thirty-second millennium, many centuries after the Horus Heresy and the Great Crusade, the Imperium still reaps the fruits of betrayal. On the planet Gangava Prim, traces of the traitor primarch Magnus the Red and his Thousand Sons, a legion of warrior-mages, are discovered. The Order of the Space Wolves is hastily equipping an army led by the Great Wolf Harek Iron Helm, for a debt to the Imperium that was not fully fulfilled in the distant past hangs like a curse on the honor of the Wolves of Fenris. And while the Iron Helm with the main forces of the order is trying to capture Gangava, Fenris himself finds himself attacked by the Thousand Sons. Magnus's presence on Gangava was only a bait, a trap, and now the demon primarch intends to brutally take revenge on the Wolves for the death of his home world - Prospero. The Lair of the Wolves, the great fortress of Fang, now has to withstand a monstrous siege. Or share the fate of Prospero.