Grindstones are special items which can be used to upgrade and enhance sub-stats on Runes. The increase amount on the sub-stat is based on the grade of the Grindstone, with each one possessing five different grades. 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 sub-stat and rune. However, the increase amount will be based on the original value of the sub-stat, meaning that higher grade Grindstones must be used to enhance a sub-stat further. In fact, players can only use another grindstone on a given substat if the final value is potentially higher than the current value. Additionally, only the primary stats on a Grindstone may be enhanced.
Grindstones are currently available as a reward drop from defeating the Raid boss Chaos Beast Khi'zar Kha'jul in the Rift of Worlds, and are sold in the Guild Magic Shop.
Grade[]
Each Grindstone possesses a grade level, which is similar to the rarity of Runes. However, unlike Runes, the grade of a Grindstone cannot be increased any further, and is instead fixed. There are five different grades:
Common (R1-R2)
Magic (R1-R3)
Rare (R2-R5)
Hero (R3-R5)- Legendary (R4-R5)
The stat increase amount is based on the grade of the Grindstone, with Legendary Grindstones offering the greatest increase, and Common Grindstones offering the least. The following table illustrates the minimum and maximum bonuses for each grade level[1].
| Grindstones | Magic | Rare | Hero | Legend |
|---|---|---|---|---|
| ATK%/DEF%/HP% | 2-5% | 3-6% | 4-7% | 5-10% |
| ATK/DEF (flat) | 6-12 | 10-18 | 12-22 | 18-30 |
| HP (flat) | 100-200 | 180-250 | 230-450 | 430-550 |
| SPD | 1-2 | 2-3 | 3-4 | 4-5 |
Enhancing a sub-stat[]
To use a Grindstone to enhance a sub-stat, players need only select the appropriate sub-stat. Once sub-stat has been enhanced, the Grindstone will disappear. The final boosted value will be a random number within the range indicated by the Grindstone. For example, applying a Grindstone with a stat increase of +3-6% on a sub-stat with original value of 6% may result in a total of 11(6+5)%.
Players may continually enhance a given sub-stat, although the stat increase will be based on the original sub-stat value. For example, applying a Grindstone with a stat increase of +3-6% on a sub-stat with a boosted value of 11% (original value of 6%) may result in a total of anywhere between 9-12%. In fact, the game will only allow another grindstone to be used if the final total is potentially higher than the current value. That means if a substat has already been boosted to the max by a 3-6% grindstone, a 4-7% grindstone would need to be used. It should be noted that additional grindstones may potentially boost a substat to a lower value than what the previous grindstone boosted.
Additionally, only the primary stats can be enhanced using a Grindstone. That means that only Attack, Defense, HP, and Speed are eligible to be enhanced, with Accuracy, Critical Rate, Critical Damage, and Resistance being excluded.
Immemorial Grindstone[]
An Immemorial Grindstone works similar to regular Grindstones, with the only difference being that they can be used on any rune type. They can only be obtained from Tartarus' Labyrinth and purchasing packs.
In other language[]
| Language | Title | Notes |
|---|---|---|
| English | Grindstone | |
| Korean | 연마석 | |
| Japanese | 練磨石 | Renma Ishi |
| Traditional Chinese | 精煉石 | |
| Simplified Chinese | 精炼石 | |
| French | Meule | |
| German | Schleifstein | |
| Russian | Шлифовальный камень | |
| Portuguese | Grindstone | |
| Spanish | Piedra de Molino | |
| Indonesian | Grindstone | |
| Malay | Batu Kisar | |
| Vietnamese | Đá Mài | |
| Thai | หินลับ |