Extermination of the Pale Fangs

The Extermination of the Pale Fangs was an Imperial excoriation campaign conducted by the Omni Legion Space Marine Chapter, alongside their allies from the Jiangshi Riders Chapter, to seek out and eradicated the Pale Fangs Renegade Space Marine Chapter.

History
The particular campaign is one of the few documented instances of the Omni Legion's involvement in the destruction of another Space Marine Chapter.

Rumors spoke of a possible betrayal by the Pale Fangs Chapter (an unconfirmed and unsubstantiated Space Wolves Successor Chapter). Once the news of the formerly loyalist Chapter's betrayal reached the High Lords of Terra it would as quickly reach the Adeptus Mechanicus. The idea of a renegade Chapter making use of the weapons and armour supplied by the Mechanicus was beyond worrisome. As a result the Hyldar System was made the target for the Omni Legion.

Posing as the remnants another Chapter who was sought to be destroyed, the 3rd and 4th Formations arrived at the Hyldar System requesting assistance in exchange for guarding the system as additional forces. The Captains of the Omni Legion confirmed that the Chapter Master intended on leading a stance against the Imperium, believing that those of his Chapter were deserving of being able to live their own lives. He himself was recently married. The Chapter wanted to be treated less like weapons and to be given the respect of being mankind's greatest defenders. The Omni Legionnaires worked to move the civilians to safer locations to avoid getting caught in with the cross-fire.

After several months of living alongside the Pale Fangs the Legionnaires picked up the signal of their void-faring forces engaged with an enemy fleet within the system. In truth this was the 1st Formation with the aid of the Imperial Navy and the Jiangshi Riders Chapter, the Pale Fang's fleet lost their communications through sabotage and psychic interference by the Omni Legion forces that posed as their allies. Unaware of this fact the forces on the planet surface didn't know their forces were being slaughtered by both the Imperium and their so-called allies. The planet's forces would be thrown into disarray as Omni Legion members begun to kill Pale Fang Astartes, they never expected this betrayal. Even the Chapter Master would see his end before he could even leave his throne room, slain by the two Omni Legion Captains while his three Pale Fang Captains were killed by the eight Omni Legion Honour Guards.

The sky would become filled with drop pods as both Omni Legion and Jiangshi Riders descended upon the world, streets would become lined with the corpses of the sons of Russ and their own Serfs. No one would be left alive in the cities around the entire planet, within a single day the entirety of the Pale Fang Chapter was slaughtered. It's assumed that the ultimate fate of the civilians of the world met their ends by the blades and bolters of the Jiangshi Riders who would have butchered them all for simply being associated with the Pale Fangs.

The weapons, armour and vehicles taken by the Omni Legion would be handed over to the Mechanicus so they may be properly cleansed. It isn't known how many made their way into the Omni Legion's Armoury.