Ruins of Darkness

Ruins of the Darkness or more commonly known as Ruins, is a location found in the combat map screen that is unlocked at Strategy Lv 2. The Ruins consists of a series of Clues, a fightable stage with multiple waves that can be challenged indefinitely.

Rewards for beating the stages includes Dolls, BP's, Flow Solutions, Mold Parts, Add-ons, Core Encryption Keys and various upgrade materials. The Ruins also contain Dolls that are exclusive to the location.

Hard Mode
In addition to the normal ruins, the ruins has a hard mode. Hard mode increased the difficulty of the stage by imposing certain conditions to enter and increasing the stats of the enemies but it also increased drop rate for limited dolls. You can only challenge hard mode stages 3 times per day.