The Genestealer Cult are watching the Tyranids race across the sector with great anticipation. Ascension is near but the Space Marines have found the Siren’s Call relic and are fighting to get it off world and onto a Rogue Trader Voidship. The Genestealer Cult have set up a blockade to stop the Space Marines while Tyranids from previous battles who have broken through are attacking from the flanks. The Tyranids are non-player units that will interact with the game and attack the closest enemy unit, both Genestealer Cult and Space Marines. Marneus Calgar has hatched a plan. Calling upon two other Chapter Masters the Space Marines carry three relics, but only one is the real one. And it is only the real relic that needs to be sent off world. Rogue Traders (npc) accompany each guard unit that is trying to get the Siren’s Call relics to the gate.