Play as a commander of the Primaris Space Marines, and wage war on all enemies within the Imperium Nihilus.

The most dangerous threats to the Emperor’s authority lie within the Black Library, a place where all knowledge of the universe is stored. A group of adventurers known as the Lost Alchemists have discovered a way to break the Black Library, threatening the whole galaxy. The Emperor is forced to send his forces to deal with the situation, and you, Commander, are assigned to lead the expedition.

Your task is to confront the Lost Alchemists and their forces, reclaiming their realm in the process.