The narrative and missions included in this book centre around the Doom of Magma City, a sprawling conflict that set the stage for the Mechanicum’s wider role in the Heresy. Linked missions and new rules for an Escalation Campaign – which tasks players with building up their forces before culminating in a final do-or-die battle – appear alongside army lists for Mechanicum Taghmata and Dark Mechanicum forces, as well as full rules for fielding armies entirely composed of Titans and Questoris Knights.