You can check out game guide on 12SKY LAST EMBER
Limit break
When enchanting an item, you must perform a limit break at +7 and +12 before you can enchant to the next level.
You can use the same equipment of same grade or the LIMIT BREAK STONE as an ingredient.
■ Perform the 1st Limit break in +7 enchanted state.
- If the 1st Limit break is successful, the equipment's ability increases - Safe enchant stage increases and the enchant stage does not fall below +7
■ Perform the 2nd Limit break in +12 enchanted state. - If the 2nd Limit break is successful, the equipment's ability increases and the enchant stage does not fall below +12 - Safe enchant stage increases and the enchant stage does not fall below +12 ※ Equipment may be destroyed when performing enchantment using 'Muk stone'.