Mule is a term used to describe a character created solely for the purpose of storing items in their inventory. This character is most commonly of the warrior class, as their strength allows them to carry the most items of all the classes in the game.
It is due to the limited inventory space and vast array of items available that many players find the need to create mules.
There are several different ways an item can be moved from one character to another.
Character to Character Trade
This method requires that the player have access to at least two computers, as only one instance of MapleStory will run on a single computer.
In order to trade with another account, one must log in on two separate computers, and have the characters meet in game, where they would then make the trade as they normally would.
The Storage NPC is shared among all characters in one account. If you were to place an item into the bank while logged in as one character, log out, then re-log in to the same account on a different character, you would find that same item sitting in the bank waiting for you.
Placing an item into storage costs between 100-150 meso, depending on which town you're in, though the banks are all connected. The bank can hold up to four items, though some versions of MapleStory allow users to buy extra slots in the Cash Shop.
Drop & Run
Note: This method is not recommended as it cannot guarantee the safety of your items.
Make sure the two characters are on the same map. Drop an item behind a foreground object, such as a portal. Log out of that account, log back in, and get the other character to retrieve the item.
It is said that the best place to perform this task is on a channel with fewer users, in a random unpopulated room of the Free Market. Another good place to drop the items is the Kerning City weapon and defence store, behind the column.