Outfits can be unlocked by progressing further in the campaign and completing certain challenges. This new DLC bring a new location outside of Paris and there are four new outfits available for unlock in the Dead Kings DLC to expand Arno’s wardrobe.
Unlock All 4 New Outfits:
Here are the locations and the guide, how you can unlock these new outfits in AC: Unity.
1# Raider Outfit:
You can unlock The Raider Outfit by opening the Initiates chest in the same room as Napoleon’s chest during the story mission called “Under Lock and Key”.
2# Guard of Franciade Outfit:
To find this white and blue outfit, you need to go to the Louis IX’s underground tomb, behind his burial chamber you will find a room with an Initiates chest in the back guarded by Raiders, open it and collect your reward.
3# Napoleon’s Artillery Outfit:
You need to collect every Napolean Bicorn collectible in the Dead Kings DLC city of Saint-Denis to unlock this outfit.
4# Iron Mask Outfit:
Iron Mask outfit can be unlocked by completing the Paris Story mission “The Eyes of the King.” After eliminating the Iron Mask loyalists at the mission start, locate and steal the three keys to the door, then unlock the room and read Louis XIV’s journal to unlock the mask.