Mere days after the loss of their home world Sotha, the Scythes of the Emperor stagger to the Chapter outpost at Miral Prime to lick their wounds and formulate a campaign of vengeance against the tyranids of Hive Fleet Kraken. Devastated and leaderless, these Space Marines now look to their only surviving officer, the reluctant Captain Thracian, for guidance. But the psychic shadow of the xenos is growing in the warp once more, and the bastion atop the Giant’s Coffin mesa may yet become the site of a most ignoble last stand...

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It's something quite unusual a story about battered and bloodied Space Marines on the back foot. Their world lost, their command structure demolished, can they hold themselves together in the face of utterly destructive aliens?