Long believing themselves persecuted by the rest of the Imperium, the Apostles of the XVII Legion spent decades nurturing rebellion, treason and even outright heresy. But for Kurta Sedda of the Order of the Third Hand, the Word Bearers' attack on Calth was... part of the problem. Finding themselves in the oppressive darkness of the planet's underworld, the Chaplain and his devout brothers must put aside all doubts and continue to wage war against the Ultramarines, no matter the ultimate cost.