Summoners War - Rune - GrindstoneGrindstones is a Special Rune type item that can be obtain randomly in the Scenario Map - Rift of Worlds when defeating a Raid boss. There's many different Grindstones, because it exist a Grindstones for each Rune Set. When using a Grindstones, it increase a Sub-Stat on the same Rune Set of the Grindstones! It exist 5 different Grades of Grindstones: Common, Magic, Rare, Hero and Legendary!
We can use as many Grindstones we want on a particular Rune, the increased value is base on the Grindstones and they are in a Range, like 2 to 5%, so if we use a Grindstones with +2 to 5% ATK on a Rune with a ATK% Sub-Stat of 8, it can become 10 to 13%, if we get the minimum 2% we can re-try later with another Grindstones to try to get more then +2%!
Rune Grindstone Available
|Available||ATK+ / ATK+% / DEF+ / DEF+% / HP+ / HP+% / SPD|
|Not Available||Accuracy+% / CRI Dmg+% / CRI Rate+% / Resistance+%|
Rune Grindstone GradeGrade Available in Rift of Worlds
Rune Grindstone Min/Max
|ATK+% / DEF+% / HP+%||2-5||3-6||4-7||5-10|
|ATK+ / DEF+||6-12||10-18||12-22||18-30|