Long ago defiled by the Imperium of Man, the eldar maiden world of Dûriel was once a glittering jewel in the crown of the Valedor System. As the tyranids of Hive Fleet Leviathan sweep through the sector consuming everything in their path, wayward Prince Yriel of Iyanden discovers that the farseers have inadvertently brought a greater threat to bear - a fragment of Hive Fleet Kraken, hurled into the warp in order to save the craftworld, has returned. The tyranid fleets cannot be allowed to combine, or their genetic legacies will merge into something even more terrible. Alongside allied forces from Craftworld Biel-Tan and even the dark eldar of Commorragh, Yriel has no choice but to fight on to the bitter end...