Medusa arrive on Glossop V

In mid 10.014M42 the arrival of the Biel Tan on Glossop V had taken the imperium by surprise and allowed the eldar to gain a foothold on the small imperial colony. However the outbreak of violence on the planet stirred into life the advance guard of the tyranid hive fleet "Medusa", as the hive mind realised that an escalation of hostilities between the eldar and imperium would inevitably lead to an escalation of forces on both sides. This was detrimental to the plans of Medusa, which had been patiently building up its biomass in order to swamp the defenders in one overwhelming assault.

Medusa's plans now changed, and on 1210.014M42 tyranid forces ambushed and slaughtered a patrol of the eldar on the plains between their own webway portal and the imperial lines. The arrival of Medusa on Glossop V caused alarm in imperial circles, but General Pollack, commander of Cerrack Nebula operations, determined that the Biel Tan were now vulnereable. He requested reinforcements, and within days a Dark Angels strike cruiser, a force of Imperial Fists and the Adeptus Mechanicus had arrived in orbit above Glossop V. The tyranids had defeated the eldar, but precipitated the start of a military build up on Glossop V which threatened their insidious plans in the Cerrack Nebula.