The Horus Heresy: Battle of Tallarn - Underworld Campaign

Beneath The Sapphire City, battle rages in the corridors and caverns of The Sightless Warren. This nightmare underworld, once a network of Imperial bunkers and stockpiles, is now occupied by the Iron Warriors and their traitorous allies. There can be no victory for the Imperial forces on Tallarn while the enemy remains entrenched in their concrete catacombs. With the support of the Iron Hands and Imperial Fists Legions, they will venture once more into The Sightless Warren to drive out the Iron Warriors, or die trying.