Treasure Chests (宝箱, Takarabako)? are a mechanic in the series.
Treasure Chests are scattered around every dungeon Flynn explores in a specific layout.
Treasure Chests are scattered around Tartarus randomly. Treasure Chests are found in almost every floor and other special Treasure Chests can be obtained after defeating a Boss inside of Tartarus.
Golden Treasure Chests also exist, Golden Treasure Chests often contain powerful weapons for every party member, Homunculus, Gems and Healing items.
Some items found in Treasure Chests exclusively may be required to complete Elizabeth's Requests.
Treasure Chests are scattered around Palaces in specific layouts. The treasure chests' positioning is fixed, and the contents of each one is pre-determined. Additionally, a treasure chest can only be opened once, and it won't reset under any circumstances. On the other hand, treasure chests can contain many different items, including weapons, armor and accessories.
Although chests can be opened simply by interacting with them, some treasure chests are locked, and will require the protagonist to craft and use a Lockpick to unlock it. Otherwise, the protagonist can craft the Eternal Lockpick, which he can use as many times without it being consumed.
In Mementos, as the layout is randomized, the layout and contents of treasure chests aren't guaranteed either, and in some cases, the same chest (with matching contents) might be discovered more than once.
Treasure Boxes are scattered around every dungeon Itsuki Aoi explores in a specific layout. They resemble double sized pyramid boxes. Normally invisible to the minimap, locked ones, which are shrouded in a red energy field will be marked on the map. To unlock them, one needs either a Treasure Key or Itsuki's Locktouch Raidant Skill.
Normally yellow, exclusive to Encore are blue-colored treasure boxes, which are found in the Area of Aspirations. Unlike normal areas, the locked treasure boxes in this Idolasphere will open only through progression of Side Stories.
As with all dungeon environmental interactions, opening a Treasure Box will despawn any Mirages on the field.