Sons of Gideon
From Warhammer 40k - Lexicanum
"The answer is self-evident, brothers. We have been called because we are the Crimson Fists, the shield-hand of Dorn. Of all the Space Marine Chapters across the Imperium, there are none more loyal than we. That is why so many of our brothers stand the Long Watch with the Ordo Xenos. That is why the Ordo Malleus called upon us to carry out the ultimate sanction on the Sons of Gideon and the Marines Vigilant when they forgot their oaths to Terra. Time and again the Inquisition has called upon us, because our honour and devotion is beyond reproach. The very fact that we were summoned from the undertaking on Beryl Ultra should underscore how serious the situation must be. It is a great honour to serve the Inquisition, and we should be proud that Chapter Master Kantor selected us for this task. We must not fail him."
The Sons of Gideon were a Renegade Space Marine Chapter. They were once loyal to the Imperium, before turning to heresy and giving into their madness. The Inquisition would later order the Crimson Fists to destroy the Sons of Gideon.