Battle of Caldera

The Battle of Caldera was a lamentable moment in the annals of the Chapter history of the Astral Serpents. In 999.M41, the world of Caldera came under attack by a Tyranid Splinter Fleet of Hive Fleet Moloch. The 8th Company of the Astral Serpents was deployed in response to the threat, however, unbeknownst the Chapter, the world of Caldera had already been infiltrated by the insidious Genestealers. When the Astartes arrived, the world erupted into insurrection, as the hidden genestealer cult revealed themselves. Despite the best efforts of the Astral Serpents, they were utterly destroyed by the dual threat of both the Tyranids and the Genstealers.

Background
The 8th Company Seer perceived that a great evil was heading for the world of Caldera, With a Astropathic message sent to Viperae the Company set of to defend Caldera. Days after arriving in system a Tyranid splinter fleet of Moloch arrived. With their arrival a genestealer uprising began causing the planets defenders to split their attention between these two grave threats. Despite their valiant effort and defense the world of Caldera was consumed by the Hive Fleet and the 8th Company was destroyed.