Uprising on Obeon

The Uprising on Obeon was a conflict that erupted due to the Alpha Legion influencing the local population to take up arms against the Imperium. A group of Custodes venturing into the Imperium Nihilus as part of the Indomitus Crusade later arrive on the planet in an attempt to restore order.

Battle Report
Responding to reports of Obeon's Mining Guild revolting and potentially turning to Chaos, a group of Custodes teleport onto the surface of Obeon. As they make their way through the ruined capital city of Obeon the group of warriors are bombarded with psychic blasts of energy, slowly whittling down the Custodes. When they reach the Obeon Mining Guild's location, the Custodes realize they have fallen into a trap laid by the Alpha Legion.

The Custodes who landed on the surface are then slaughtered by a group of Alpha Legionnaires and Tsek Kau, a Thousand Sons psyker collaborating with the Alpha Legion. With minimal casualties, the Alpha Legionnaires manage to push back the Custodes long enough for Tsek Kau to escape with a relic unearthed by the Obeon miners.

The surviving Custodes make a tactical retreat back to their ship to call for reinforcements.