Mule

From FFXI Wiki

A mule or an alt is an alternate character created expressly for supporting the player's primary character by holding additional items or gathering resources. A player can create up to fifteen mules to support the primary character for USD $1/£0.70 more per mule added to the monthly rate to play the game.

Japanese players use the word "souko" (倉庫, storehouse, warehouse) for mule characters.