You can upgrade the star ratings of your heroes by visiting the Advancement Sanctum and choosing to evolve a hero. Only heroes that have been enhanced to the highest level of their relevant star tier can be evolved.
Tip: Evolution Ginseng is a rare item that can help with evolution. You can use Evolution Ginseng as one of your heroes to fuse with for the evolution process, or to help rapidly enhance heroes to their highest level.
To evolve your hero and upgrade the star rating, you will need:
|Hero's Initial Amount of Stars||Evolve to||Amount of heroes needed|
|2 star hero||3 star hero||2 x 2 star heroes|
|3 star hero||4 star hero||3 x 3 star heroes|
|4 star hero||5 star hero||4 x 4 star heroes|
|5 star hero||6 star hero||5 x 5 star heroes|