Once you have enough soulstones you will be able to "Evolve" your hero. Evolving your hero greatly increases your hero's stats and increases your STAR ranking by one. If you don't have enough soulstones, tap on the "+" sign and on the right it will show you where you can gather more soulstones. Sometimes certain soulstones may also be available for purchase in General Store, Arena Store, Sky Arena Store, Pirate Store, and Camex Store. If you do not see a place for gathering these items, it means we are currently working on new chapters. You will be able to gather them once new chapters are released.