MU Online Season 4: When Socket Items Arrived

MU Online Season 4 introduced socket items, the build-your-own gear system that is still part of Season 22. It went live on the Korean service in August 2008 with socket weapons and armor, seed spheres, the Raklion hunting ground with its raid boss Selupan, and new skills for every class. A follow-up in April 2009 added Vulcanus, the Duel Arena and the merchant Moss, and the global service later released its version of that update, headlined by Vulcanus and Moss, as Season 4.5.

Season 4 at a glance

• Korean service: Season 4 on August 26, 2008; the Vulcanus update on April 2, 2009.
• Global service: Season 4 with Webzen's own relaunch in mid-2009; Season 4.5 in February 2010.
• Classes: still six, with the Summoner from Season 3 as the newest.
• New maps: Raklion (La Cleon in Webzen's 2009 global beta), Vulcanus with the Duel Arena, and a Christmas Santa Village.
• Headline systems: socket items and seed spheres, new skills for every class, and new master-level skills.
• Level cap: unchanged at 400, with up to 200 Master Levels on top.

What is the difference between Season 4 and Season 4.5?

Season 4.5 is a global name, not a Korean one. Korea released Season 4 in August 2008. In April 2009 it followed with an update named after its new map, the Ruins of Vulcanus, which brought Vulcanus, the Duel Arena and Moss. The global service got both later, as two separate releases: Season 4 with Webzen's relaunch in mid-2009, then the update it called Season 4.5 in February 2010. Webzen's Season 4.5 notice named Vulcanus and Moss as its two headline additions.

Community version lists blur the line further and sometimes file sockets and Raklion under "Season 4.5" as well. On the Korean timeline, sockets and Raklion belong to Season 4, while Vulcanus, the Duel Arena and Moss arrived together in April 2009.

How the 2009 relaunch brought Season 4 to global players

K2 Network operated the global service under a Webzen license from 2006 until the contract ended in May 2009. Webzen then took the service back and opened a new Season 4 realm, after a three-day beta at the end of April. In the beta press release, Master Level, Illusion Temple and La Cleon were listed as content the global version had never had, so older Korean additions reached global players in the same step as Season 4.

How did socket items work in Season 4?

Sockets let players add bonuses to their gear themselves, piece by piece. The Season 4 rules:

• Seeds are extracted from excellent or set items of +4 or higher, at a cost in jewels and Zen.
• Spheres only drop from monsters.
• Two NPCs in Elbeland, the Seed Master and the Seed Researcher, combine seeds and spheres into seed spheres and fit them into socket gear.
• The slot decides the element. Weapons take fire, ice and lightning; armor takes water, wind and earth.
• Order and outfit matter. A bonus option depends on the order of the spheres, and set options look at the whole outfit.

Webzen tied the system to its new boss from day one: Korea's launch event promised a set of three seed spheres to the first player on each server to bring Selupan down.

Sockets never left the game. Season XI's global Part 2 let seed spheres be upgraded up to level 10, Season 21 Part 2-2 raised the success rates for enhancing socket items, and the socket item files remain in the Season 22 package IGCN ships. Our socket guide walks through seed spheres, options and upgrades.

What is Raklion, and how did the Selupan raid work?

Raklion, spelled La Cleon in Webzen's 2009 global announcement, is reached from Devias and opened at level 270 (180 for the Magic Gladiator and Dark Lord). The map has a safe zone, a hunting ground and a hatchery. In the Season 4 design its boss, Selupan, only appeared after players broke the spider eggs in the hatchery, so every raid started by clearing the nest. Once Selupan was out, latecomers had five minutes to get in before the hatchery entrance closed.

Raklion is still the doorway to modern content. In Season 21 Part 2-2, Korea opened Raklion of Oblivion, a level-1650 hunting ground entered from inside Raklion, and the original hatchery event survives in IGCN's Season 22 data.

What else did Season 4 add?

New skills for every class

Webzen billed Season 4 as the first update to give every class new skills at once, plus new master-level skills for characters past the 3rd class change. Korea's Season 4 character notes list Strike of Destruction for the Dark Knight line, Expansion of Wizardry for the Dark Wizard line, Multi-Shot and Recovery (an SD heal) for the Elf, Flame Strike and Gigantic Storm for the Magic Gladiator, and Chaotic Diseier for the Dark Lord, all learned from orbs, books and scrolls dropped by monsters of level 100 and up. The Summoner got Lightning Shock, Berserker and the Book of Lagle with its Pollution spell.

Santa Village

From December 16 to 30, 2008, Korea opened the Santa Village for Christmas. Santa NPCs handed out buffs and gifts, including a ring that turns you into a snowman. The global service opened it with Season 6-3 in December 2011.

What did the Vulcanus update, or Season 4.5, add?

Korea's April 2009 update added three things. Its global release, Season 4.5, was announced with Vulcanus and Moss as the headline content.

• Vulcanus, open from level 30 (20 for the Magic Gladiator and Dark Lord), was billed as a PvP field: outside its safe zone, killing players brought no PK penalty or outlaw status.
• The Duel Arena became the home of every duel, with up to four duels running per server. Spectators enter through Titus, the gatekeeper in Vulcanus. Winners get the 60-minute Gladiator's Honor buff, which works only in Vulcanus: 20% more EXP (not for master-level characters) and a chance at better drops from its monsters.
• Moss, a new merchant in Elbeland (Moss the Gambler in Webzen's global guides), sells excellent and rare items.

Vulcanus is still on the map in Season 22, and Season 18 built on its lore: Ignis Volcano, a level-1220 hunting ground at launch, is home to magma-covered monsters that Webzen's story traces to the depths below Vulcanus. Our PvP guide covers duels and the PK rules as they work today.

MU Online Season 4 FAQ

What is MU Online Season 4.5?

The global service's name for its release of Korea's April 2009 Vulcanus update, which in Korea brought the Vulcanus map, the Duel Arena and the merchant Moss. Global players got it in February 2010, announced with Vulcanus and Moss; Korea never used the name.

When were socket items added to MU Online?

With Season 4, on the Korean service in August 2008. Seeds and spheres combine into seed spheres, which go into socket weapons and armor.

Was there a new class in MU Online Season 4?

No. Season 4 gave the existing classes new skills instead, and the class count held at six, with the Summoner from Season 3 as the newest. The next class, the Rage Fighter, arrived with Season 6 in October 2010.

Are there Season 4 private servers in 2026?

A few. On one MU server list we checked on November 3, 2026, Season 4 was a rare tag, far behind Season 6. Sockets, Raklion and Vulcanus are also part of any Season 6 Episode 3 build.

Season 4's systems today, and where SilverMU stands

Season 22 still uses the socket system that Season 4 started, and Raklion is still the way into Raklion of Oblivion. SilverMU's test realm is on Season 22 Part 1-1, release 22.1.1.0 of the files, which carries all of that forward along with all 16 classes. The seasons on either side are Season 3 and Season 5, and our MU Online season history places every season on a single timeline.

The realm is in testing for now. When rates and settings are final, a news post will say so first, and when the client is ready, it goes on the download page. Signing up costs nothing.