The Gage Chivalry Pack Add-on for PAYDAY 2 has 4 achievements.
Complete any heist on the OVERKILL difficulty or above with 4 players using only Gage Chivalry Pack masks, primary weapons, melee weapons and Ballistic Vests or heavier armors. Unlocks the "Agatha Knight Veteran" mask, "Bloodied" material and "Agatha" pattern.