Treasure Chests are available after the completion of Raids and Hardcore Instanced missions and Operations. Opening the Chests may grant a re-roll of the mission's loot table and/or a Fragment.
- Hardcore missions/operations chests, called 'Medium ARES Chest', requires 2 Security Keys to be opened;
- Raid chests, called 'Large ARES Chest', requires 5 Security Keys to be opened;
- Any squad member may use as many keys as he'd like. Once all keys are inserted, everyone still in the instance gets the reward;
- Opening a Raid's Chest will also grant an extra Titan Token. The weekly limit does not apply to this, so while you'll only get 1 normal reward and Titan Token per week, you can get as many Titan Tokens as you'd like by completing Raids and opening it's chests.
Treasure Cache's screenshot uploaded by DarkByke at the Official Forums