War on Kronus

The War on Kronus was a conflict between the T'au Farsight Enclaves and the Adeptus Custodes. Taking advantage of the carnage, the Alpha Legion later landed on the planet to acquire Necron technology.

Battle Report
In the middle of a firefight between the Farsight Enclaves and the Custodes, the T'au notice a group of Alpha Legion marines making their way across the battlefield along with a single Thousand Sons sorcerer. Believing them to be Imperial reinforcements, the T'au open fire on them, wounding and killing a handful of the Alpha Legionnaires. The marines quickly return fire before taking cover and seemingly vanishing out of sight.

As quickly as they disappeared, the renegade marines sudden reappear near the left and right flanks of the Farsight Enclave's forces and attack. A great number of T'au warriors fall to this surprise attack before a golden light appears from behind the Alpha Legionnaires. From the golden light charges a squad of Custodians led by their Shield Captain. The Custodians cut through countless Alpha Legionnaires but amidst the carnage the Alpha Legion Chaos Lord seemingly vanished. For the rest of the battle the Alpha Legion are nowhere to be seen, presumably leaving the planet to return on a more peaceful day.

Despite being outnumbered, the Custodes forces stand their ground until the T'au forces deem the battle a waste of resources and leave the planet.