MU Online Mysterious Stone Guide – Mastery Set & Weapon Options

Mysterious Stone is a special item used to reroll the hidden options of Mastery items in MU Online (Bloodangel, Darkangel, Holyangel, Awakening, Blue Eye, Silver Heart, Manticore, Brilliant, Apocalypse, Lightning, etc.). It is one of the key tools for min‑maxing your end‑game gear in Season 20 and Season 21 style servers.

This guide explains in simple English:

  • What Mysterious Stone does and how to use it.
  • All possible Mastery armor options (All Stats +7/+15 and damage reduction).
  • All possible Mastery weapon options and their chance rates.
  • How Mastery Bonus options work and when Mysterious Stone stops changing them.
Quick summary: Mysterious Stone randomly changes the special Mastery options on your Mastery armor and weapons. It can make your item much stronger (for example All Stats +15 + Luck & Reduce Damage +75 on armor), but it can also remove Luck or give you worse options, so use it carefully.

What Is Mysterious Stone?

Mysterious Stone is an item that:

  • Randomly changes the current option of a Mastery item.
  • Works on Mastery set armors and weapons (and shields, if they have Mastery options).
  • Can be stored in vault, traded with other players and sold to NPC shops.

Where you get the Mysterious Stone depends on the server (events, promos, shops, etc.), but its behaviour on Mastery items is the same: it rerolls the Mastery Additional Option and sometimes the Mastery Bonus Option.

How to Use Mysterious Stone

Using Mysterious Stone is very simple:

  1. Put the Mastery item (armor or weapon) in your inventory.
  2. Place the Mysterious Stone in your inventory as well.
  3. Drag and drop the Mysterious Stone onto the Mastery item.
  4. Click OK to confirm the reroll.
Important: The result is completely random. The options can stay the same, get better or become worse. You can also lose Luck when rerolling, so never use Mysterious Stone on an item you are not prepared to risk.

Mastery Set Options (Armor)

When you use a Mysterious Stone on a Mastery armor piece (helm, armor, pants, gloves, boots), it affects two layers of special options:

  • Mastery Additional Options – “All Stats +7/15” and Luck.
  • Mastery Bonus Options – extra damage reduction.

Mastery Additional Options (Armor)

These are the possible Additional options on a Mastery set piece:

  • Increases All Stats +7
  • Increases All Stats +7 / Luck
  • Increases All Stats +15
  • Increases All Stats +15 / Luck ← Best Additional option

All Stats +15 / Luck is the strongest Additional option you can get on a Mastery armor piece, and this is what most players try to roll with Mysterious Stone.

Mastery Bonus Options (Armor)

The Bonus options on Mastery armor give extra damage reduction:

  • - (no bonus)
  • Reduce DMG by 25
  • Reduce DMG by 50
  • Reduce DMG by 75 ← Best Bonus option

When using a Mysterious Stone, the chance to get each Mastery Bonus option on armor is:

Mastery Armor Bonus Option Chance
No bonus ( - ) 85%
Reduce DMG by 25 7%
Reduce DMG by 50 6%
Reduce DMG by 75 2%
Goal for armor:
Best case is Increases All Stats +15 / Luck as your Mastery Additional option and Reduce DMG by 75 as your Mastery Bonus option.

Mastery Weapon Options

Mastery weapons also have a special set of Additional and Bonus options. Mysterious Stone can reroll these, including Luck, making your weapon much stronger if you hit one of the rare combinations.

Mastery Additional Options (Weapon)

All Mastery weapon options always include Increase Excellent Damage Chance plus one or more extra effects:

  • Increase Excellent Damage Chance + Increase attacking speed
  • Increase Excellent Damage Chance + Increases per every 20Levels (ATK/WIZ/Curse per 20 levels)
  • Increase Excellent Damage Chance + Attack DMG
  • Increase Excellent Damage Chance + Obtains (Life/8) when monster is killed
  • Increase Excellent Damage Chance + Obtains (Mana/8) when monster is killed
  • Increase Excellent Damage Chance + Increase attacking speed + increases per every 20Levels
  • Increase Excellent Damage Chance + Increase attacking speed + Luck
  • Increase Excellent Damage Chance + increases per every 20Levels + Luck
  • Increase Excellent Damage Chance + Attack DMG + Luck
  • Increase Excellent Damage Chance + Obtains (Life/8) when monster is killed + Luck
  • Increase Excellent Damage Chance + Obtains (Mana/8) when monster is killed + Luck
  • Increase Excellent Damage Chance + Increase attacking speed + increases per every 20Levels + Luck

When using a Mysterious Stone on a Mastery weapon, the chance for each Additional option is:

Mastery Weapon Additional Option Chance
Increase Excellent Damage Chance + Increase attacking speed 11%
Increase Excellent Damage Chance + Increases per every 20Levels 4%
Increase Excellent Damage Chance + Attack DMG 26%
Increase Excellent Damage Chance + Obtains (Life/8) when monster is killed 26%
Increase Excellent Damage Chance + Obtains (Mana/8) when monster is killed 26%
Increase Excellent Damage Chance + Increase attacking speed + increases per every 20Levels 1%
Increase Excellent Damage Chance + Increase attacking speed + Luck 0.5%
Increase Excellent Damage Chance + Increases per every 20Levels + Luck 2%
Increase Excellent Damage Chance + Attack DMG + Luck 1%
Increase Excellent Damage Chance + Obtains (Life/8) when monster is killed + Luck 1%
Increase Excellent Damage Chance + Obtains (Mana/8) when monster is killed + Luck 1%
Increase Excellent Damage Chance + Increase attacking speed + increases per every 20Levels + Luck 0.05%
Goal for weapons:
The most “perfect” roll is Increase Excellent Damage Chance + Increase attacking speed + increases per every 20Levels + Luck with only 0.05% chance. Any 2–3 option combination with Luck (Attack DMG, Life/Mana on kill) is already very strong.

Mastery Bonus Options (Weapon)

Weapons can also roll a Mastery Bonus option that increases your stats directly. These are separate from the Additional options above:

  • - (no bonus)
  • All Stats +10
  • All Stats +25
  • All Stats +40 ← Best Bonus option

The chance for each Mastery Bonus option on weapons is not listed in the in‑game UI, but All Stats +40 is extremely rare compared to lower bonuses or no bonus.

How Mastery Bonus Options Behave with Mysterious Stone

There are three important rules to remember about Mastery Additional and Mastery Bonus options:

  1. Bonus options are very rare.
    Mastery Bonus options (Damage Reduction on armor, All Stats +10/25/40 on weapons) have very low probability and can also appear when you first create or transform a Mastery item.
  2. Best Additional option can become “locked”.
    If you manage to roll the best Mastery Additional option (for example All Stats +15 / Luck on armor, or a top triple option on weapons), the game can lock that Additional option. After that, when you use Mysterious Stone again, only the Mastery Bonus option will be rerolled.
  3. When both Additional and Bonus are max, you’re done.
    Once a Mastery item has both the highest Additional and the highest Bonus option, you can no longer use Mysterious Stone on it – the item is considered “perfect” and the game will not let you change it again.
Practical tip: If you get a god‑tier Additional option (for example a rare weapon roll with Luck) but a weak Bonus option, it is usually worth continuing to use Mysterious Stones only to improve the Bonus. Your Additional option will not be changed anymore once it is locked at its best value.

When to Use (and Not Use) Mysterious Stone

Good times to use Mysterious Stone

  • On end‑game Mastery gear you plan to keep for a long time (Apocalypse, Lightning, etc.).
  • When your item has bad options (no Luck, low stats, no bonus) and you want a chance to hit something strong.
  • On high‑value weapons where even “medium” rolls (Attack DMG + Luck, Life/Mana on kill + Luck) are a big upgrade.

Times to be careful or avoid using it

  • If your item already has Luck and a decent Additional option and you don’t want to risk losing them.
  • If you don’t have enough stones to realistically aim for a high roll.
  • On low‑tier Mastery gear you will soon replace with higher sets (e.g. Bloodangel that will be upgraded to Darkangel/Holyangel soon).

Conclusion

Mysterious Stone is one of the strongest and most dangerous upgrade tools in MU Online. It can turn an ordinary Mastery item into a true end‑game piece with All Stats +15 / Luck, high damage reduction and rare triple weapon options, but it can also remove Luck or give you worse rolls.

Use Mysterious Stones on items you really care about, aim for the best Additional option first, and then slowly chase the perfect Mastery Bonus option. With patience (and a bit of luck), you can create some of the most powerful gear possible in Season 21.