Pack yaks also have a special ability called, "Winter Storage". By using an item on your Pack yak, it will be instantly sent to your bank.
Because of all of the Pack yak's uses, they are very helpful. You can send bones to your bank while killing Frost dragons, or when running from pk'ers. You can also use the right-click option and do, "Take all" and get items stored in your yak out while being in combat.
"Winter Storage" is the Pack yak's special ability. If a player uses an item on their summoned Pack yak, it will instantly bank that used item, without the player needing to visit an actual bank. This is particularly useful for various activities such as skilling, PvP , as well as PvM activities.
It is important to note that Winter Storage can only be activated once every 10 seconds. This prevents players from massively banking items where it may be an unfair advantage, such as during PvP activities.