Muun, pets and modern companions in MU Online: complete guide

Muun are Season 12's companion system — miniature creatures that appear alongside your character, providing real passive bonuses while occupying an entirely different slot than regular pets. They transform end-game S12+ optimization from "only gear" into a multi-axis system.

What Muun are

Muun overview:

Muun: small creature companions introduced in Season 12
→ They visually appear on or near the character (floating, walking alongside, etc.)
→ Different visual sizes and styles based on Muun type
→ Visual difference from regular pets: more compact, different positioning

What makes Muun more than cosmetics:
→ Each Muun provides one or more passive bonuses (always active)
→ The bonus magnitude: scales with Muun rarity tier
→ These bonuses: stack with gear, Excellent options, and regular pet bonuses

Muun slot vs pet slot:
→ Regular pets (Dinorant, Fenrir): occupy the Pet equipment slot
→ Muun: occupy their own dedicated Muun/Companion slot(s)
→ Some characters: unlock multiple Muun slots at higher levels or evolution tiers
→ Having Fenrir AND a Muun simultaneously = both bonuses active

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How Muun bonuses work:

The bonus is always passive:
→ No activation needed: as long as the Muun is equipped, bonus is active
→ The bonus applies 24/7 during gameplay
→ It's the same mechanic as a stat-bonus accessory, but in companion form

Example passive bonuses:
→ +X% damage increase
→ +X defense
→ +X HP
→ +X attack speed
→ +X% critical hit chance
→ Specific elemental resistances
→ The exact bonus type: depends on the individual Muun

Multiple Muun slots:
→ If the character has 2+ Muun slots: both Muun bonuses apply
→ Stack: Muun 1 + Muun 2 = total of both bonuses
→ Multiple Muun slots are unlocked through character evolution quests on S12+ servers

Muun rarity tiers

The four rarity tiers:

COMMON (white/grey):
→ Obtainable from: most S12+ events and boss drops
→ Bonus magnitude: small (3-5% on typical bonuses)
→ Investment to obtain: low effort
→ Value: accessible early S12+ improvement — get these immediately
→ Example: +50 HP, or +3% physical damage

UNCOMMON (green):
→ Obtainable from: better S12+ events, dedicated farming
→ Bonus magnitude: moderate (6-10% range)
→ Investment to obtain: moderate farming
→ Value: solid mid-game companion that holds for a while
→ Example: +100 HP, or +6% physical damage, or +50 mana

RARE (blue):
→ Obtainable from: boss drops (S12+ bosses), events, trading with players
→ Bonus magnitude: significant (12-18% range on damage-type bonuses)
→ Investment to obtain: requires dedicated end-game farming or market purchase
→ Value: meaningful power boost; worth pursuing as an end-game goal
→ Example: +200 HP + bonus defense, or +12% damage + +5% critical

EPIC (purple/gold):
→ Obtainable from: rare boss drops, specific events, combination (server-specific)
→ Bonus magnitude: large (20%+ on major bonuses, or multiple bonuses)
→ Investment to obtain: significant end-game time investment
→ Value: among the most impactful single items in S12+ optimization
→ Example: +15% all damage + +300 HP + +8% defense

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Rarity comparison table:

Rarity | HP example | Damage example | How to get
Common | +50 HP | +3% Damage | Most events, basic farming
Uncommon | +100 HP | +6% Damage | Regular S12+ events
Rare | +200 HP | +12% Damage | Boss drops, trading
Epic | +350+ HP | +20%+ Damage | Rare drops, end-game events

How to obtain Muun

Primary Muun sources (S12+ servers):

1. Events:
→ Blood Castle (S12+ version): rewards Muun based on performance
→ Devil Square (S12+ version): Muun as possible reward
→ Special event periods: higher chance of Rare Muun
→ Seasonal events: may award specific themed Muun

2. Boss drops:
→ S12+ bosses (Phoenix of Darkness, Lord of Ferea, etc.): may drop Muun
→ Boss drop quality: generally Uncommon-Rare tier
→ Epic Muun from bosses: very low drop rate

3. Ruud Merchant NPC:
→ Some Common/Uncommon Muun: purchasable with Ruud currency
→ Daily/weekly Ruud income → accumulate for Muun purchases
→ Higher rarity Muun: typically not available from Ruud shop (drop-only)

4. Player trading (market):
→ Any Muun can be bought from other players
→ Common Muun: cheap (small Zen/JoB amount)
→ Epic Muun: very expensive (among the most valuable tradeable items)

5. Muun combination (server-specific):
→ Some servers: combine multiple lower-rarity Muun for a chance at higher rarity
→ Example: 3× Uncommon Muun + JoC → 1× Rare Muun (with success rate)
→ Verify if your server has this recipe before spending Muun

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Muun priority by stage:

Early S12+ (just entering the season):
→ Grab any Common Muun from the first events
→ Even Common: better than no Muun
→ Don't spend much Zen/Ruud on Common Muun — farm them

Mid S12+:
→ Target Uncommon Muun from regular event participation
→ Begin farming S12+ bosses for chance at Rare drops
→ Check Ruud shop weekly for Muun options

End-game S12+:
→ Target Rare Muun specifically from top-tier bosses
→ Save Ruud for the best Muun the shop offers
→ Epic Muun: only if accessible — don't spend excessive resources on the first Epic

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Which Muun bonus to prioritize:

The goal: match the Muun bonus to what your class needs most

Dark Knight:
→ Priority: damage Muun + HP Muun
→ Best: Epic with % damage + HP combination

Dark Wizard:
→ Priority: magic damage Muun + HP Muun (DW is fragile)
→ Best: whatever provides the highest magic damage bonus

Fairy Elf:
→ Attack Elf: damage/speed Muun
→ Support Elf: HP Muun (survival while buffing)

Magic Gladiator:
→ Priority: damage Muun (scales both physical and magical paths)

Dark Lord:
→ Priority: damage Muun + defense Muun (frontline survivability)

Summoner:
→ Priority: magic damage Muun + HP Muun (fragile magic class)

Muun vs classic pets: the relationship

How Muun and classic pets coexist:

In S12+ content, a character can have:
→ Slot 1 (Pet): Fenrir Black (or Dinorant, etc.) — classic pet
→ Slot 2+ (Muun): 1-2 Muun companions — modern system

Both are active simultaneously:
→ Fenrir Black: flying + defense + no-knockback immunity + pet attack
→ Muun (Rare): +12% damage + +200 HP (passive always-on)
→ Total: all of Fenrir's benefits + all of the Muun's benefits

Neither replaces the other:
→ There's no reason NOT to have both
→ Priority: get the classic pet first (Fenrir route: requires more work)
→ Then: start the Muun system (begins with easy Common Muun from events)

Combined S12+ power optimization:
→ Character stats (level + reset + stats)
→ Gear (weapon + armor + accessories + upgrade level + Excellent options)
→ Wings (L1/L2/L3 depending on server tier)
→ Classic pet (Fenrir Black ideally)
→ Pentagram + Errtels (5-slot elemental system)
→ Muun (1-2 companion slots)
→ Jewel of Harmony on gear
→ Seed Spheres in sockets

Muun is ONE layer in a multi-axis system. Treat it as one component, not the only priority.

See also the Fenrir pet guide (the S6+ classic pet that coexists with Muun), the Pentagram and Errtels guide (the other S12 power system), and the Ruud currency guide (the S12 currency used to buy some Muun).

Frequently asked questions