Here is the full list of all 10 Legacy of Sin the father sacrifice achievements.
Have 1/3 Pikeman, 1/3 Arquebusiers and 1/3 Knights in your army.
Summon 30 Pikeman.
Summon 20 Arquebusiers.
Summon 10 Knights.
Build 50 Barricades.
Win a game with only Pikeman.
Win a game with only Arquebusiers.
Win a game with only Knights.
Finish the game.
Defeat 100 enemies.