Battle for the Abyss

"My brother, my enemy"

- Book's tag-line

Battle for the Abyss is the eighth book in the Horus Heresy series

Plot Summary
Battle for the Abyss describes the lead-up to the Battle of Calth fought between Primarch Roboute Guilliman 's Ultramarines and the Word Bearers Traitor Legion. The Word Bearers plan to use an immense warship, the Furious Abyss, to spearhead their attack. The protagonists must pursue the ship and prevent it from reaching Macragge, the Realm of Ultramar's capital world.

If the Ultramarines break and give way to the traitorous Word Bearers, Guilliman's Legion will suffer a blow they may never recover from.