During the Battle for caliban, as the furious single combat between two erstwhile friends and brothers, The Lion and Luther, climaxed, Caliban itself shuddered under the furious bombardment of the enraged loyal Dark Angels. Every fortress monastary was demolished except the main fortress, where Jonson battled Luther. As Jonson restrained himself from striking down Luther fatally, Luther unleashed a psychic attack that mortally wounded the Primarch. Seeing the agony of his friend, the veil of pretence lifted and Luther collapsed next to the lion, realising his folly. The Dark Gods, realising that, once again, they had lost, lashed out by creating a massive warp storm. The weakened state of the planet was unable to withstand such unnatural fury, and crumbled in to debris. The entire planet was demolished and sucked in to the warp. All except for the Fortress Monastary, that we today know as the Rock , which had been protected by massive force fields.
The survivimg fallen angels were sucked in to the warp and scattered not only throughout the galaxy, but also through time. The fallen angels who are even today being hunted by the Dark Angels are the same ones who fought alongside Luther. They do not follow any particular chaos deity. Some roam as bands, others as individuals. Some have managed to integrate themselves in to society and liev a double life, ever fearful of the avenging deathwing. others roam as mercenaries, bandits or guns for hire.
The Dark Angels follow up every possible lead towards the capture of one of the fallen, even at the potential expense of the safety of the imperium. It is their secret agenda. But intelligence and sightings of the fallen are far and few in between. Mostly sketchy details or holo-vid accounts, which are too late to be of much use. Here are some of he Fallen being tracked by the Interrogator Chaplains of the Fortress!!