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Crusader Kings 2 is on sale for 75% off as the Steam daily deal for 10/16/12.
Crusader Kings II = $9.99 / £7.49 / €9.99
Crusader Kings II: Dynasty Shields = $0.49 / £0.39 / €0.49
Crusader Kings II: Mongol Faces = $0.49 / £0.39 / €0.49