The Hive Mind had by this point targeted Calgar as the main threat to the Tyranid advance. The Swarmlord, the Hive Mind's deadliest servant, was dispatched to deal with him. The arrival of this unique beast was the turning point of the battle, for the defenders were beginning to grasp the near-mindless, rampaging way in which the swarms attacked, but now the Swarmlord's influence infused the Tyranids with a keen strategy. The defender's left flank was suddenly assaulted by tunneling Raveners, which only served as a diversion to lead the Ultramarines away from the Swarmlord's true target - the Pride of Hera. The Baneblade was left wide open for a wave of Carnifexes to rip it apart. Calgar watched as his enemy's tactics unfolded. Gargoyles and Harpies preyed upon officers and sergeants of the Auxilia units. Biovores bombarded the defenders and forced them to spread out to minimize casualties, but this in turn left them vulnerable to Mawloc and Trygon attacks. The Ultramarines reacted to each threat with valor and bolstered weakened sections of their line; however they were outnumbered and outmatched. Then the Swarmlord, with a bodyguard of Tyrant Guard and Tyranid Warriors, bellowed a challenge to Calgar and charged directly towards his position. The Ultramarines rushed to aid their Chapter Master, but even this movement was planned for by the Swarmlord. Hundreds of apparently dead Hormagants strewn across the ground leapt to sudden life and bogged down the Space Marines, delaying them from reaching Calgar. The Ultramarines Honour Guard could not stop the Swarmlord from renting, tearing and gravely wounding Calgar. Just in time, Thunderhawk Gunships arrived from orbit and blasted the Tyranids back to clear enough room to land and evacuate the survivors. Commander of the Guard Aloysius held back the Swarmlord and its attending Tyrant Guard as the rest of the Honour Guard helped Calgar to safety. Just as Aloysius fell to the Swarmlord's blades, the Thunderhawks lifted off to return to the Battle Barge Octavius in orbit above Macragge. Cold Steel Ridge was taken by the Tyranids, leaving the path to the northern polar fortress clear.