Grindstone | Summoners War Sky Arena Wiki | Fandom
Grindstone values are based on ranges, with the final boost value being a random number in the displayed range. Players can use Grindstones multiple times on a given substat and rune. However, the increase amount will be based on the original value of the substat, meaning that higher grade Grindstones must be used to enhance a substat further. In fact, players can only use another ...