Permanent and non-repeatable game mode in NIKKE where you can unlock Harmony Cubes and get rewards as you clear every Lost Sector. It’s unlocked after clearing 5-3 in the main campaign, and you can see the requisites for every Lost Sector in the main screen.
You can also preview all the rewards for the next available Lost Sector and the completion reward if you clear 100% of it. We recommend clearing every level as you unlock them, Harmony Cubes are an important part of the builds of your characters.