"Battle for the Abyss" is a continuation of the epic tale of the Horus Heresy, which entailed a brutal confrontation in a galactic civil war that could lead to the complete destruction of humanity. The Warmaster's betrayal became clear, and for the people who remained loyal to the Emperor, the time of difficult trials came. One of the pillars of the Imperium is under threat - the Ultramar system, the home world of the Ultramarines Legion, towards which the fleet of the Word Bearers Legion is heading. The flagship of this campaign is a monstrous ship built at the secret Mechanicum shipyard, the Furious Abyss, which has never been equaled. And only by pure chance does the defenders of Ultramar become aware of this threat. Several warships of different Space Marine Legions, who, by the will of fate, find themselves on the path of the “Abyss”, choose the disastrous for themselves, but the only possible path - to fight.