The Gage Chivalry Pack Add-on for PAYDAY 2 has 4 achievements.
Kill a Cloaker with the Javelin throwable. Unlocks the "Mason Knight Veteran" mask, "Scale Armor" material and "Mason" pattern.
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.
Kill a black Bulldozer with the Great Sword melee weapon. Unlocks the "Mason Vanguard Veteran" mask, "Forged" material and "Checkered Out" pattern.
Kill 10 shields with a Gage Chivalry Pack melee weapon in a single heist. Unlocks the "Agatha Vanguard Veteran" mask, "Chain Armor" material and "Medieval" pattern.