Shatters arm

Magnus drove his fist into Russ' chest, the icy breastplate breaking open with a sound like planets colliding, and shards of ceramite stabbed the Wolf King's heart. In return, Russ snapped Magnus' arm back, and Ahriman heard it shatter into a thousand pieces. A blade of pure thought unsheathed from Magnus' other arm, and he drove it deep into Russ' chest through his shattered armour.

Thousand Sons pg. 261