Last updated: August 18, 2026

On this page: Why Season 4 · Socket System · Seed Options · Bonus & Set Options · Socket Gear · Raklion & Selupan · New Skills · Master Rank 4 · FAQ

MU Online Season 4 – Socket System, Raklion & Selupan

Season 4 (August 2008) started the modern gear era: the socket system let players build custom item options for the first time, the frozen spider kingdom Raklion arrived with its boss Selupan, every class received new signature skills, and the master tree grew its rank 4 row. Rebuilt here from the original patch notes, with the original artwork.

Why People Still Play Season 4

Reason	Detail
Sockets without the bloat	Season 4 introduced the socket system — deep gear customisation while the game was still recognisably classic. Many players consider it the best balance point.
Raklion & Selupan	The spider boss remains one of MU's best-designed raid fights, and socket gear drops only there — giving endgame a real destination.
The sweet spot	More content than Seasons 1–3, none of the Season 6+ systems to balance — a popular middle ground for mid-rate servers.
Classic roster	Six classes through Summoner, before the roster expansion — simpler balance, cleaner PvP.

Choosing between classics: Season 2 for the hardest grind, Season 4 for sockets, or Season 6 for the fullest classic package.

The Socket System – Original Rules

The flow is Extraction → Synthesis → Mounting → Destruction, run by two new Elbeland NPCs. Seeds, spheres and seed spheres are fully tradeable and storable.

Seed Master — extraction & synthesis	Seed Researcher — mounting & destruction

Step	NPC	Materials	On failure
1. Extraction	Seed Master	+4+ excellent or set item + Harmony + Chaos + Creation + zen	Item drops to +0–+2, jewels destroyed
2. Synthesis	Seed Master	Seed + Sphere (monster drop) + Chaos + Creation + zen	All materials lost
3. Mounting	Seed Researcher	Socket item + Seed Sphere + Chaos + Creation + zen	—
4. Destruction	Seed Researcher	Item + zen only	Sphere destroyed, socket freed

The pieces, as drawn in 2008: a raw Sphere (monster drop, useless alone) fuses with a Seed into a Seed Sphere that carries the option into the socket. Element rules from day one: Fire, Ice, Lightning seeds go into weapons; Water, Wind, Earth into armor. Season 4 shipped with a single sphere grade — the Mono–Penta ladder came later.

Seed Option Pools (Original)

	Element	Slot	Options
	Fire	Weapon	ATK/wizardry per level, attack speed, max ATK, min ATK, flat ATK, AG cost −
	Lightning	Weapon	Excellent DMG +, excellent DMG rate, critical DMG +, critical DMG rate
	Ice	Weapon	HP on kill, mana on kill, skill attack +, attack rate +, durability +
	Water	Armor	Defense rate +, defense +, shield defense +, damage decrease, damage reflect
	Wind	Armor	HP auto-regen, max HP, max mana, mana regen, max AG, AG value +
	Earth	Armor	Vitality/stamina +

Bonus & Set Socket Options

The original patch notes documented the exact order-dependent combos (30% proc chance at mounting):

Gear	Mount order	Bonus option
Melee/ranged weapons & scepters	Fire → Lightning → Ice	Attack power +11
Melee/ranged weapons & scepters	Lightning → Ice → Fire	Skill attack +11
Staffs	Fire → Lightning → Ice	ATK/wizardry +5
Armor pieces & shields	Water → Earth → Wind	Defense +24
Armor pieces & shields	Earth → Wind → Water	Max HP +29

And the set socket options, counted across everything you wear (100% when the counts match): one seed sphere of every element = double damage chance +3%; the deeper 1–3–1–3–1–2 spread (Fire/Water/Ice/Wind/Lightning/Earth) = ignore defense +1%. Modern crafting values live in the socket system guide.

The Socket Gear (drops only in Raklion)

Socket items drop with 1–3 sockets rolled forever at drop, carrying normal-style bonus options (ATK/DEF/wizardry/luck/HP recovery). All require level 380. Original 2008 concept art:

	Weapon	Class	ATK / notes
	Flameberge	Blade Knight	106–117, speed 40
	Sword Breaker	Blade Knight	91–99, speed 35
	Rune Bastard Sword	Magic Gladiator	98–122, speed 45, +109 wizardry
	Deadly Staff	Magic Gladiator	+126 wizardry
	Frost Mace	Muse Elf	106–146, speed 50
	Dark Stinger	Muse Elf	162–184 two-hand bow, speed 45
	Absolute Scepter	Dark Lord	114–132, pet ATK +72%
	Inberial Staff	Soul Master	+124 wizardry

	Shield	Class	DEF / rate
	Crimson Glory	Blade Knight	19 / 90
	Frost Barrier	Muse Elf	14 / 58
	Guardian Shield	Soul Master	12 / 55
	Salamander Shield	Magic Gladiator	12 / 55

	Set	Class		Set	Class
	Titan	Blade Knight		Brave	Blade Knight
	Hades	Soul Master		Royal	Dark Lord
	Divine	Muse Elf		Seraphim	Muse Elf
	Phantom	Magic Gladiator		Destroy	Magic Gladiator

Raklion & the Selupan Fight

The frozen map connects to Devias: entry level 270+ (180+ for MG/DL), /move at 280+ for 15,000 zen. It layers from safe zone through the hunting fields into the Hatchery — Selupan's lair.

	Monster	Lvl	HP	ATK	DEF
	Ice Walker	102	68,000	1,310–1,965	615
	Giant Mammoth	112	77,000	1,441–2,017	585
	Ice Giant	122	84,000	1,585–2,060	620
	Coolutin	132	88,000	1,743–2,092	650
	Iron Knight	142	95,000	1,917–2,301	660
	Selupan (boss)	145	4,800,000	?	? (def rate 1,800)

The fight: destroying the spider eggs inside the Hatchery summons Selupan. The entrance stays open for 5 minutes after he appears, then seals — latecomers are locked out and whoever is inside splits his high-grade socket loot. His mixed heavy attacks made him the first boss where the def-rate stat (1,800) mattered more than raw defense. Selupan camps became the standard guild evening activity of the S4–S6 era.

New Class Skills

Learned from orbs, books and scrolls dropped by monsters level 100+ — with their original icons:

	Skill	Class	Req	Effect
	Strike of Destruction	Blade Knight+	lvl 220	Ice strike — slows the target's movement
	Expansion of Wizardry	Soul Master+	ENE 1058	+min wizardry buff for 30 minutes
	Multi-Shot	Muse Elf+	lvl 220	5 piercing arrows
	Recovery	Muse Elf+	lvl 220, ENE 168	Heals target's SD
	Flame Strike	Magic Gladiator	lvl 220	Fire-imbued blade strike
	Gigantic Storm	Magic Gladiator	ENE 1058	Lightning AoE around the caster
	Chaotic Diseier	Dark Lord	lvl 220, ENE 84	Dark AoE damage
	Lightning Shock	Summoner	lvl 93, ENE 823	Lightning AoE around the caster
	Berserker	Summoner	lvl 83, ENE 620	Curse/wizardry/ATK/MP up — defense & HP down
	Pollution	Summoner	lvl 85, ENE 557, Book of Lagle	Corrupts an area: slows and damages everything inside

The Third Summon: Lagle

Lagle — bringer of misfortune from the otherworld Karun	Book of Lagle — unlocks Pollution	Demonic set & Demonic Stick

Wherever Lagle appears, plague and decay follow — his Pollution zone slows and damages every monster inside, giving the Summoner true AoE farming. The budget Demonic Stick (drop 100, +92 wizardry) and Demonic set rounded out her mid-game gear.

Master Tree Rank 4

The master tree gained its rank 4 row: max SD and SD recovery speed, max/min attack and wizardry increases (MG's wizardry nodes also raise attack), mana cost reduction, pet durability preservation for Dark Lords — and per-class strengtheners (Evil Spirit and Ice line for casters, Power Slash for MG, Fire Scream for DL, defense/attack rows for Elves). Weapon skills became learnable without the weapon equipped, usable once armed.

The same update also rebuilt the event schedule into the half-hourly rotation of Blood Castle / Chaos Castle / Devil Square / Illusion Temple that servers still run variants of today.

Continue Reading

Guide	Why it helps
Socket system	The modern, full version of this mechanic.
Season 3 guide	The Summoner/Master Level era right before.
Season 2 guide	Kanturu and the harmony system this builds on.
Master skill tree	Where rank 4 fits in the modern trees.
Excellent options	The extraction fodder economy sockets created.

FAQ

Where can I play Season 4?
Browse the Season 4 private servers currently listed — and most Season 6 servers run this exact socket system too.

Why do socket items only drop in Raklion?
Original design — Raklion was the socket economy's only source in Season 4. Later seasons spread socket drops across boss and event loot.

Extraction ruined my excellent item — is that normal?
Yes: failed extraction knocks the material item down to +0–+2 and destroys all three jewels. It was MU's original item sink.

Is Berserker worth it on Summoner?
It defined her from Season 4 on: massive damage for massive fragility. Farming yes, sieges only with a pocket healer.