Complete the indicated task to unlock the achievement.

Achievement	How to unlock
Chapter I - Complete	Complete all Chapter I Missions.
Chapter II - Complete	Complete all Chapter II Missions.
Chapter III - Complete	Complete all Chapter III Missions.
Contempt Maintained	Complete Forges of Corruption on My Armour Is Contempt Difficulty.
Defeat a Great Unclean One	Defeat a Great Unclean One.
Defeat a Lord of Change	Defeat a Lord of Change.
Duty Fulfilled	Complete Horde Mode on Emperor's Mercy Difficulty.
Emperor's Mercy	Complete all Missions on Emperor's Mercy Difficulty.
Exterminatus	Complete all Missions on Exterminatus Difficulty.
Find All Secrets - Forges of Corruption	Find all secrets in Forges of Corruption.
Find all Secrets - Chapter 1	Find all Secrets in Chapter 1.
Find all Secrets - Chapter 2	Find all Secrets in Chapter 2.
Find all Secrets - Chapter 3	Find all Secrets in Chapter 3.
For the Emperor!	Complete Horde Mode on Exterminatus Difficulty.
Let None Survive	Complete Horde Mode on any difficulty.
Mercy Extended	Complete Forges of Corruption on Emperor's Mercy Difficulty.
My Armour is Contempt	Complete all Missions on My Armour is Contempt Difficulty.
Rage Incarnate	Defeat a Helbrute.
The Emperor Protects	Complete all Missions on The Emperor Protects Difficulty.
The Emperor Still Protects	Complete Forges of Corruption on The Emperor Protects Difficulty.
There Is Only War	Complete Forges of Corruption on Exterminatus Difficulty.