When the world of Shadrac was attacked by the Tyranids, one of the Space Wolves' Great Companies attempted to defend it, and when it became clear that this effort was in vain, Skold Greypelt and his Pack decided to remain behind with the assistance of an Iron Priest and his Thunderhawk gunship, to inflict as many losses as possible on the Tyranids and make them pay the heaviest possible price for the Imperium's loss of the doomed world.