Iben Purge

The Lben Purge was the lamentable conflict that occurred to the Void Paladins Space Marine Chapter when they began delving too much into the forbidden knowledge in regards to the secular, atheistic philosophy known as the Imperial Truth that was once espoused by the Emperor and his forces during the Great Crusade era. Unwilling to let an upstart Adeptus Astartes Chapter learn the truth and spread lies about the Imperial Cult, the Ecclesiarchy and their allies in the Ordo Hereticus, launched a pre-emptive strike upon the Void Paladins Chapter Homeworld, to silence them. The few remaining survivors fled the destruction of their homeworld and were later declared renegades in absentia.

Background
Vicious assault conducted by Ecclesiarchy and Inquisition forces against the chapters homeworld in an effort to extinguish them before they started asking around about the Imperial Truth. This force consisted of a dozen trooper regiments, multiple Sororitas companies, & several senior Inquisitors as the commanders transported by a large fleet of warships. Most of the force is wiped out in the ensuing battle but most of its inner core escapes when the naval battle turns to the Paladins' favor. Entrenched positions were left alone during the defection so as to not provoke them and any prisoners were locked in a barracks with supplies and a vox. Afterwards the Inquisition used virus bombs to kill any Paladins Astartes and Ibeni that stayed behind, this also claims the lives of most of the surviving remnants of the disastrous first assault who had been assumed butchered in its aftermath.