The 15th Anniversary balloon was a reward obtained during the 15 Year Anniversary Celebrations. The balloon could be used to bank one single item. If stackable items were used on it, it would only bank one. After banking an item, this ability had a cooldown of 30 minutes. The cooldown was also triggered when destroyed and reclaimed. It was unlocked by popping 50 balloons in the balloon drop part of the event. The balloon was removed on 1 February 2016.
The 15th Anniversary balloon allowed for some quest items, such as Karamja rum, to be banked in order to move them outside the bounds of a given quest.
It allowed banking up to level 30 of the Wilderness.
Because of the cooldown, the balloon's banking feature was useful if a player was collecting items without banking for over one hour, so that at least two items could be banked. Otherwise, the feature could only be used once, effectively saving one inventory space by using up one as well.