As of now, the Traitors have effectively lost one legion (Thousand Sons, Prospero.) And Three are badly Mauled - * Night Lords (Thramas Crusade) * World Eaters (Isstavan + Ultramar) * Emperor's Children (Lost half their legion in Isstavan + Losses in the eye and against at the Perfect Fort) More than, that * Alpha Legion loyalty unknown. Either way, they go AWOL by the end. * Death Guard also suffered at Isstavan * Word Bearers mauled fighting in Ultramar Compare Loyalists - Only four legions down, Salamanders, Iron Hands, Raven Guard and Ultramarines. And their not even completely out.