MU Online Glossary: Terms Every Player Should Know
Last updated: 10 July 2026
This glossary defines the MU Online terms you will meet on server websites, toplists, Discord channels and guide pages, from reset and Grand Reset to Ruud, sockets and wipe policies. Values marked on RiftMu are this network's settings; everything else is labelled as official behaviour or common private-server practice.
Progression
Reset - Returning a character to level 1 in exchange for permanent stat points or bonuses, then levelling again. Resets are the core progression loop [Common on private servers]; the official service does not use them. On RiftMu you reset with the /reset command, and VIP 5+ accounts can automate it with /reset auto. See the reset guide for requirements and strategy.
Grand Reset (GR) - A milestone that consumes your accumulated resets for a larger permanent reward. On RiftMu a Grand Reset requires 20 resets, level 400 and 50,000,000 Zen, and grants Grand Reset Points: 1 per reset counted, capped at 20.
Grand Reset Points (GRP) - The currency earned from Grand Resets. On RiftMu you can exchange GRP at 15,000 WCoinC per point, up to 20 exchanges per day, provided you have recent Blood Castle, Devil Square or Chaos Castle participation and your daily quest done.
Master Level - Post-400 levels that feed the Master Skill Tree with passive and active skill upgrades [Official].
Majestic Level - A later extension of the post-400 system with its own skill tree, added in the Season 16 era [Official].
EXP rate - The experience multiplier compared to the official pace. RiftMu's Permanent Realm runs 5000x; the Speed Realm Summer Edition runs 99,999x. Rates only make sense alongside stat caps and reset rules, never alone.
Max stats - The cap on each stat (Strength, Agility, Vitality, Energy, Command). Both RiftMu realms cap stats at 60,000. Caps decide when a build is finished and how far gear matters beyond stats.
Items and upgrading
Excellent item - An item with special bonus options such as increased damage rate or mana on kill, shown with a green name [Official]. The backbone of mid-game gearing; see the upgrading guide.
Ancient item - A set item with hidden bonuses that unlock as you equip more pieces of the same set [Official]. Strong for PvP builds at certain stat thresholds.
Socket item - Weapons and armour with sockets that accept Seed Spheres for customisable bonuses, introduced in Season 4 [Official].
Harmony option - A bonus option added with the Jewel of Harmony and strengthened with refining materials [Official].
Ruud - A bound currency earned from events and bosses, spent on Ruud shop gear including mastery-tier sets and weapons, introduced in the Season 12 era [Official].
Luck - An item option that adds critical damage chance and improves Jewel of Soul success odds on that item [Official].
Skill option - A weapon option meaning the weapon carries its special attack skill built in [Official].
Wings - Back items crafted in the Chaos Machine that add damage and damage absorption; higher wing tiers are major power spikes [Official].
Pentagram and Errtel - The elemental damage system: pentagrams are equippable items, errtels are the upgrades slotted into them, introduced in the Season 9 era [Official]. Central to Arca War maps.
The classic jewels come up constantly in trade chat, so here is the quick reference [Official behaviour; drop rates vary by server]:
| Jewel | What it does |
|---|---|
| Jewel of Bless | Raises an item's level by 1, safely up to +6. |
| Jewel of Soul | Raises an item's level by 1 with a chance to fail; Luck on the item improves the odds. |
| Jewel of Chaos | Core ingredient for Chaos Machine combinations: wings, higher item levels, event tickets. |
| Jewel of Life | Adds or raises the bonus additional option on an item, with a chance to fail. |
| Jewel of Creation | Ingredient for Chaos Machine recipes such as Fruits, which grant stat points. |
Beyond the classics, RiftMu adds a custom jewel ladder: Helix, Gold Helix, Kingz, High Kingz, Emperor, Supreme, Volt and Vibrant. The new jewels guide covers each tier; the Emperor Jewel's Combo Ring upgrade has its own guide.
Events and PvP
PK (Player Killer) - Killing players outside sanctioned PvP, which builds murderer status and penalties [Official]. On RiftMu you can clear kill counts with the /pkclear command.
PvP - Player-versus-player combat, from open-field duels to structured sieges. Start with the PvP guide.
PvE / PvM - Player-versus-environment (or versus-monster): levelling, hunting and boss fights. Note that Elf PvM is intentionally weaker on RiftMu's Speed Realm.
Castle Siege - The weekly guild-versus-guild war for control of the castle and its perks; on RiftMu it runs weekly around the Land of Trials and Loren battlefield. See the Castle Siege guide.
Blood Castle - A timed instance where a party fights to the top of a castle to recover an archangel's weapon [Official]. Registration opens shortly before each start; live times are on the events page. Full walkthrough in the Blood Castle guide.
Devil Square - A survival event where waves of monsters spawn in an arena and rewards scale with kills [Official].
Chaos Castle - A last-player-standing event mixing PvP and monster kills on a shrinking floor [Official]; see the Chaos Castle guide.
Gens - The two-faction system, Duprian and Vanert, enabling faction PvP and contribution rewards [Official].
Arca War - Scheduled guild battles fought with pentagram elemental damage; on RiftMu it runs several times per week across three zones: Alkmaar, Ubaid and Debenter.
Server types
Private server - An independently hosted MU Online server, separate from the official Webzen service, usually with custom rates and systems. RiftMu is a Season 21 (Part 3 era) private server.
Low / mid / high rate - Loose community bands for EXP multipliers. There is no fixed standard [varies by community], but low rate usually means slow, near-official pacing, while high rate means resets in hours, not weeks.
Speed server - A very high rate server built around fast cycles and quick gearing. RiftMu's Speed Realm Summer Edition (99,999x EXP) is one, with a Blood Angel set in the starting inventory.
Seasonal realm - A world that opens, runs for a limited period, then closes, often with progress carried elsewhere afterwards.
Permanent realm - A world with no planned end. RiftMu's Permanent Realm (5000x EXP) never closes and has no wipes.
Wipe - A full deletion of characters and items, usually before a relaunch. Always check a server's wipe policy before investing time.
No-wipe - A commitment that progress is never deleted. It is only as good as the server's track record.
Fresh / grand opening - The launch day of a new server or realm, when everyone starts equal. The RiftMu Speed Realm Summer Edition opened on Friday 10 July 2026 at 16:00 CEST.
Pay-to-win (P2W) - A server where purchases grant power that cannot reasonably be earned in game. Judge by whether paid items are also obtainable through play.
Vote reward - Currency or perks paid for voting on toplists [Common on private servers]. How the whole system works is covered in the MU Top 100 guide.
RiftMu-specific terms
GP - RiftMu's web currency. The base rate is 470,000 GP per euro (940,000 during the Summer promotion), and world bosses like Kingz Dragon drop it too on the Permanent Realm.
WCoins - An in-game currency earned from events and bosses on RiftMu; the WCoinC variant is what GRP exchanges pay out.
Vote Points (VP) - Earned at 1 per verified MU Top 100 vote (one per 12 hours) plus link-sharing bonuses, and spent in the VIP Vote Shop: VIP3 is 100 VP for 14 days, VIP4 is 315 VP for 21 days, VIP5 is 1,260 VP for 30 days.
Volt Jewel - An end-game upgrade jewel used mainly on White Dragon-tier items to create Volt and Fury gear [Season 21 era; private implementations vary]. On RiftMu, the Supreme to 100% White Dragon conversion is boosted.
Vibrant Jewel - A rare RiftMu jewel with a drop chance from Kingz Dragon and the Giant Treasure.
Dreadnaught - RiftMu's anti-cheat system, running alongside the client. If the game will not start, check the startup troubleshooting guide.
Speed Realm export - When the Speed Realm Summer Edition closes after its few-week run, each player can export 2 characters to the Permanent Realm, keeping their progress - the design that makes it a catch-up path for newer players.
Common mistakes
- Reading EXP rates in isolation. A 99,999x realm is not simply a faster 5000x realm; the endgame structure differs. Compare stat caps and reset rules together.
- Confusing reset with Grand Reset. A reset is the routine loop; a Grand Reset consumes 20 resets (on RiftMu) for a bigger milestone reward. Spending resets carelessly delays your GR.
- Mixing up GP and WCoins. GP is RiftMu's web currency; WCoins are earned and spent in game. Prices quoted in one are not convertible one-to-one into the other.
- Assuming official values apply everywhere. Drop rates, upgrade odds and event schedules are tuned per server. When a guide labels something [Official], expect private servers to differ.
- Treating rate bands as standards. One community's mid rate is another's high rate; check the actual multiplier.