>>24791274It's basically this game's equivalent of evolution. You can do it when a puppet reaches Lv 30.
The puppet can become one of 2 out of 4 styles: Speed, Power, Defense, and Assist. The style chosen determines what stats are raised, can give you a new ability to use, and can also change a puppet's type.
While each puppet currently has only 2 options out of the 4 styles, the expansion coming at the end of the month will give you all four options.
Unlike evolution, this can be reversed by reincarnation, which sets your puppet back to Lv 1 and reverts its style to Normal, allowing you to raise it again in the other/a new style. How to do reincarnation and what is retained is unknown to me since I haven't reached that point in the game yet.
