Remnant: From the Ashes – How to Unlock New Game+ Mode
Successfully complete the story and defeat the final boss. Once the final boss is defeated, return to Ward 13 and activate the Red Stone. You will then have the option to increase the difficulty and Reroll at this location. Rerolling will reset the world and make it much more difficult. Elite enemies are much more likely to spawn, regular enemies will be more difficult, and Lumenite Crystals will drop more commonly.
Lumenite Crystals are special rare items that you can use to craft/upgrade Boss weapons. Boss weapons are special weapons that drop from bosses, and can be acquired by defeating bosses using alternate methods. Lumenite Crystals can also upgrade your Dragon Heart charges. You can get an unlimited number of charges by replaying New Game+ and collecting Simulacrum and Lumenite Crystals.