Here is the full list of all 16 The Horus Heresy: Battle of Tallarn - there are Iron Edition achievements.
Destroy 3 enemies without a loss
Destroy 1 Warlord
Destroy 1 Warlords
Destroy 1 Knight
Destroy 10 Knights
Destroy 8 enemies without a loss
Destroy 12 enemies without a loss
Complete 10 scenarios on hard difficulty
Complete 30 scenarios on hard difficulty
Complete the Tutorial Campaign
Complete Apocalypse Campaign as Loyalist
Complete Apocalypse Campaign as Traitor
Complete Resurrection Campaign as Loyalist
Complete Resurrection Campaign as Traitor
Complete Revenge Campaign as Loyalist
Complete Revenge Campaign as Traitor