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Gnosis Prime was the main world of the Gnosis system, orbiting the star Gnosis Aurora. The planet served as the main industrial hub of the entire Talhor Sector, its fifty billion citizens toiling in expansive manufactora whose choking pollution left the planet's atmosphere and oceans toxic. As a result, sustenance for the population was farmed on the nearby moon Gnosis Secundus, nutritious plant mulch farmed by workers who dreamt of one day visiting Prime's vast hives.[2a]
In 838.M41, Gnosis Prime was invaded by a force of Eldar led by the Autarch Eliac Zephyrblade, mostly from the craftworlds of Saim-Hann and Biel-tan.[1c] Zephyrblade gave the Imperial population only one day to evacuate the planet. Its governor, Ulyx, dismissed this as an idle threat; confident that his Planetary Defence Forces, bolstered by Cadian and Valhallan regiments, could keep the world secure. Zephyrblade's forces made use of webway portals to bypass and encircle these forces, culling the populace until scant few survivors remained.1a: .
Space Marines of the Space Wolves chapter, led by Logan Grimnar, were close to the system when they received a distress call, and immediately set out to defend Gnosis Prime. However, a warp anomaly caused their fleet to enter the system a year after they set out, preventing them from aiding the beleaguered world. Instead, Grimnar turned his focus to rescuing Gnosis Secundus, eager to avenge the dead.[2b]