From the battle records of the Adamant Cabal, temporarily unsealed by order of Inquisitor [REDACTED].
After a harrowing, skin-of-the-teeth defense by the forces of the Imperium (the result of first crusade), the forces of Chaos succeeded in ensuring the Adamant Cathedral collided with the planet with its nearly full mass (the result of the second crusade).
Once the stone shell of the space hulk had burnt away during atmospheric entry and cracked open on impact, it was revealed to be the husk of a long forgotten Aeldari craftworld.
The spirit stones were corrupted after such prolonged exposure to the energies of the immaterium, turning the Infinity Circuit of the ship into a warbling beacon of psychic screams and attracting the daemonic forces en masse. The forces of the Imperium worked tirelessly to try to end the threat, but each step forward was met by two backwards as the forces of Great Enemy pushed back, and forces acting in their own best interest undermined both sides at nearly every turn.
In the end, there could only be one outcome – while the force of the Imperium wouldn’t be able to save the planet, the forces of chaos hadn’t succeeded in plunging it into the warp and seeing the Shroud rip further to connect with the Cicatrix Maledictum and cut off potential escape routes from the Realm of Ultramar’s 500 worlds…
Instead, the planet would suffer a slow death by strangulation as the psychic screams of the craftworld’s corpse called more and more daemons until such day the Imperium can someday spare the resources necessary to turn this once pristine chapel world to dust. Until then, the once blazing bonfire of the Emperor’s Light will flicker until it eventually sputters out like a campfire in monsoon.