MU Online Inventory & Vault Expansion Guide – Magic Backpack & Vault Expansion Certificate

Starting from Season 6 Part 2, MU Online added an option to expand your inventory and vault using two special items: Magic Backpack and Vault Expansion Certificate. This system is still used on modern Season 20 & Season 21 servers, including MUOnline.ai, and works for all classes.

You will learn:

• How inventory & vault expansion works in MU Online.
• How to buy and use Magic Backpack to get more inventory space.
• How to buy and use Vault Expansion Certificate to unlock a second vault.
• About quest‑based alternatives with Wandering Merchant Zyro on some servers.

1. How Inventory & Vault Expansion Works

Base inventory & expanded inventory

By default your character has a single inventory grid (the classic one you open with the I key). With the expansion system:

• You can unlock up to two extra inventory pages using Magic Backpack.
• Each Magic Backpack adds an extra page of 8×4 slots.
• So in total: main inventory + 2 × 8×4 expanded pages.
• On modern clients these pages are usually shown as: Inventory, Inventory 1, Inventory 2 or similar tabs.

Base vault & expanded vault

Your account also has a vault (storage), which you open at the Storage NPC (Vault Keeper). With the expansion system:

• You can unlock one extra vault using a Vault Expansion Certificate.
• The extra vault adds another grid of 8×15 slots.
• You switch between Vault 1 and Vault 2 using a button in the vault window (or arrows, depending on client).
• Each account can usually expand the vault only once.

2. Inventory Expansion with Magic Backpack (Mu Item Shop)

The easiest and most common way to expand inventory on Season 6+ and Season 20–21 servers is by buying the Magic Backpack from the Mu Item Shop (X‑Shop).

Requirements

• Character on any class / race.
• Enough WCoin (or WCoin(P), Goblin Points, etc. depending on server).
• On some servers: minimum character level (often 150+ or 300+).

Step‑by‑step: how to buy and use Magic Backpack

1. Open the Mu Item Shop
   While in town, press the X key to open the Mu Item Shop window.
2. Find Magic Backpack
   Go to the GENERAL tab and look for the item Magic Backpack.
3. Buy the Magic Backpack
   Click the BUY button/icon.
   A confirmation window will show the price and your current WCoin balance. Check you have enough WCoin and click BUY again.
4. Confirm the purchase
   The system will show a message like “Purchase completed”. Click OK to close the confirmation.
5. Open X‑Shop Storage
   In the Item Shop window, go to the STORAGE (or “Purchased Items”) tab. You will see the Magic Backpack there.
6. Use the Magic Backpack
   Select the Magic Backpack and click the USE button.
   A description popup appears. Read it and click OK to confirm.
7. Confirm activation
   The system will show that the Magic Backpack has been used. Click OK. The item disappears from Storage and the expansion is now linked to your character.
8. Relog to apply the expansion
   Most servers ask you to switch character or re‑log to apply the change. Follow the prompt, then log back into your character.
9. Open your expanded inventory
   Press I and look for the extra inventory tabs or icons such as: “Open Expanded Inventory”, “Inventory 1”, “Inventory 2”.

3. Vault Expansion with Vault Expansion Certificate (Mu Item Shop)

To expand your vault, you need the item Vault Expansion Certificate. Like the Magic Backpack, it is typically bought in the Mu Item Shop.

Requirements

• Any character on the account (vault is shared).
• Enough WCoin or equivalent currency.
• Some servers require level 50+ before you can expand the vault.

Step‑by‑step: how to buy and use Vault Expansion Certificate

1. Open the Mu Item Shop
   Press X in town to open the shop.
2. Find Vault Expansion Certificate
   Go to the GENERAL tab and look for Vault Expansion Certificate.
3. Buy the Vault Expansion Certificate
   Click BUY. Check the price and your WCoin, then click BUY again to confirm.
4. Confirm purchase
   When the system says the purchase was successful, click OK.
5. Open X‑Shop Storage
   In the Item Shop window, go to the STORAGE tab and find the Vault Expansion Certificate.
6. Use the Vault Expansion Certificate
   Select it, click USE, read the info popup and click OK to confirm.
7. Confirm activation & relog
   The game will show that the item is used and recommend re‑logging. Click OK, then change character or restart the game.
8. Open the second vault
   Talk to the Vault Keeper (Storage NPC) and open storage.
   You should now see a way to switch between Vault 1 and Vault 2 (button, arrows or a small tab).

4. How to Use Expanded Inventory & Vault

Using expanded inventory

• Press I to open your inventory.
• Click the small icons or tabs (for example: “Inventory 1”, “Inventory 2”) to switch between pages.
• On most servers:
  • Your main inventory fills first.
  • When it is full, the game starts filling Expanded Inventory 1.
  • Once that is full, it starts using Expanded Inventory 2.
• You can move items between pages simply by dragging them.

Using the second vault

• Talk to the Vault Keeper (Storage NPC) and open your storage.
• Look for a Vault 1 / Vault 2 switch, or left/right arrows.
• Click to swap between your base vault and the expanded vault.
• Use Vault 2 for:
  • Spare sets, extra wings, jewels and event items.
  • Shared gear you move between characters via vault.

5. Quest Method – Wandering Merchant Zyro (Alternative)

Some Season 6–21 servers also offer an alternative method: quests with Wandering Merchant Zyro. Instead of buying items from the X‑Shop, you complete quests to earn Magic Backpacks and Vault Expansion Certificates.

Where to find Wandering Merchant Zyro

On servers that use this system, Wandering Merchant Zyro appears in:

• Lorencia – around (131, 138)
• Noria – around (186, 109)
• Devias – around (226, 52)
• Elbeland – around (55, 199)

Typical quests for expansion

Quest	Required Level	Quest Item	Drop Location	Reward
Vault Expansion – Ancient Statue	Level 50+	Ancient Statue	Lost Tower 6–7 (Death Knight, etc.)	Vault Expansion Certificate
Inventory Expansion 1 – Magic Cloth	Level 150+	Magic Cloth	Atlans 2–3 (Silver Valkyrie, etc.)	Magic Backpack (adds 2nd inventory 8×4)
Inventory Expansion 2 – Space Cloth	Level 300+	Space Cloth	Icarus (Alquamos, etc.)	Magic Backpack (adds 3rd inventory 8×4)

Once you get the Magic Backpack / Vault Expansion Certificate from Zyro, you use them exactly like the items from the X‑Shop: right‑click or “Use” them and relog to apply the expansion.

6. FAQ & Practical Tips

Is inventory / vault expansion the same for every class?

Yes. Inventory size and vault size are account features, not class features. A Dark Knight, Elf, Summoner, Rune Mage, Slayer, Gun Crusher, White Wizard, Lemuria Mage, Illusion Knight, Alchemist or Crusader all expand in exactly the same way.

What happens if I delete the character?

On most servers, Magic Backpack expansions are tied to the character. If you delete the character, its expanded inventory pages are lost. Vault expansion is tied to the account and remains as long as the account exists.

Can I trade Magic Backpack or Vault Expansion Certificate?

Usually no. In official MU and most Season 20+ private servers, these items are non‑tradable to prevent market abuse. Check the item tooltip – if it says “Cannot be traded”, you must use it yourself.

What should I put into expanded inventory vs. vault?

• Use Expanded Inventory for items you need while hunting: extra potions, scrolls, jewels, spare weapons or events drops.
• Use your vault for long‑term storage: finished sets, wings, rare jewels, crafting materials, event rewards.

Why should I expand early?

A bigger inventory and vault:

• Lets you farm longer without going back to town.
• Makes it easier to keep extra sets, jewels and crafting items.
• Reduces the chance you drop or sell valuable items by mistake.

Use this Inventory & Vault Expansion guide together with your Upgrade Guide, Skill Drop Guide and Wings Guide to make your character progression smoother on MUOnline.ai and any modern MU Online server.