NIKKE Lost Sector Guide: Dungeon-Crawl Treasure Runs & the Gateway to Harmony Cubes

Lost Sector unlocks after Campaign Stage 5-3. Initially only the first Sector is available; further Sectors unlock progressively as you advance through the Campaign. The core loop: guide your squad through a node map, choose which path to take, collect treasure along the way, and reach the end point for rewards.

You can send your squad back to the starting point to swap Nikkes between battles within the same run. The key difference from Simulation Room: a Nikke's status (HP, remaining buffs, etc.) does NOT carry over between those battles — each battle inside a Lost Sector effectively starts fresh. Some Sectors go further and require deploying more than one squad at once, letting you freely switch control between them during the run.

Conquering Lost Sectors is the main way to UNLOCK Harmony Cube types. Once unlocked, leveling a cube requires a Battery item specific to that cube type — Batteries come from Lost Sector itself, or can be bought at the Union Shop at a rate of 1 Battery per 200 Union Chips. Per one source, the total Batteries needed to level a cube to max (level 15) is 1,020 Batteries — this figure hasn't been cross-checked against a second source, so treat it as a reference point that needs further verification before treating it as a hard number in the final public article.

Lost Sector isn't the only Battery source: clearing bosses in Solo Raid also drops Batteries, with the amount depending on the boss level defeated; drops are random and capped at 6 Batteries per day through that channel — see the Solo Raid article for details.