Black Oculus (The Horus Heresy #Short Story)

After Fulgrim's ascension to daemonhood at Iydris, Perturabo and his Legion were trapped by the singularity at the heart of the so-called 'Eye of Terror'. Their only option? To thread the needle, and dive into the heart of the black hole. Perhaps by sheer blind luck, they were transported far across the warp to the Tallarn System but the Navigators in service to the Iron Warriors fleet were irreversibly corrupted by that harrowing experience. Now they serve a new purpose, and Perturabo's plans for revenge come closer to fruition... Read it because
Bridging the gap between Angel Exterminatus and the Battle of Tallarn, this short story focuses on the Navigators assigned to Iron Warrior Legion fleet. After their journey through the Eye of Terror, many of their number are... changed. This story also contains some hints as to the Iron Warriors motivation for their attack on Tallarn.