"This Act of Heresy shatters all ties of kinship. Those I was proud to call Brother I now fight to bloody death. No quarter will be asked and none sought. These are the vilest foes we must fight. There shall be no peace, no rest, no succour until the face of Horus stares down from Traitor's Gibbet and all his Heretic followers are vanquished."

— Anonymous Loyalist, Istvaan III Atrocity

The Waning moon a Strike Cruiser of the fifteenth Legion, a battle damage and near crippled vessel speeds threw the warp for Terra. Its crew a rag tag band of legiones astartes from those Legions who denounced the Emperor and the Imperium, race to warn the Emperor of the treachery that has occurred.

occupied by the remnants of brothers from several different Legions the Waning Moon is set to suffer its darkest hour. From within betrayal strikes, casting those aside once more in violent destruction. Now the Istvaan III Atrocity is set to repeat itself in microcosm. Out numbered the loyalists have fought a bitter struggle to halt their traitorous kin but to no avail.

All they have managed is to relocate their struggle to a world of peace and harmony, to Equestria. Their bitter struggle will escalate and not even the Princesses hold the power in which to halt such terrible destruction.

The lines have been drawn, one side righteous and loyal the other heinous and chaotic, will Equestria survive? Only if they choose the right side.