Adeptus Titanicus2 books in series
Warlord: Fury of the Godmachine Publisher's Summary
The Battle Titans of the Adeptus Titanicus are towering war engines, striding to war as holy effigies of the Omnissiah. Greatest of all are the mighty Warlord Titans, their weapons bringing righteous death to alien and heretic alike. Still reeling from a near disastrous battle against tyranids, the Pallidus Morr demi-legio is assigned to a new warzone, a nearby forge world which has fallen under the sway of Chaos.
Here their battered war-machines must fight alongside another Titan Legion, the Imperial Hunters. As city after city falls before the relentless tread of Chaos war machines, the Imperium's only chance of victory lies in the two legios putting aside their differences and fighting as one.