Rebirth gives a permanent upgrade for a character that will increase their combat functionality. After a one-star character reaches their maximum level of 30, spend gold and a few special items to boost them to a two-star rank. The cost to use Rebirth on that character again will increase. Being Reborn allows a character to keep their level 30 stats, which are also slightly increased, but resets them to level 1 to allow them to become even stronger. This also unlocks new skills and allows access to more powerful weapons.