Backpack of Shrinking

The Backpack of Shrinking looks like a well made normal backpack. However it was originally a large backpack with a permanent double shrink spell enchanted into it so that anything approaching within 1" of it's opening is shrunk in size by a factor of 4.

• Instead of holding the usual 1 cubic foot or 30 pounds of gear, it can instead hold up to 64 cubic feet / 1920 pounds of gear, although it will weigh less than 31 lbs as the volume and weight of each item in the pack is decreased by a factor of 64.
• Anything larger than 6' in any dimension and wider than 4' at its narrowest will not fit in the backpack.
• Since the backpack doesn't use extra-dimensional spaces like a bag of holding it is safe to use in rope tricks and the like.
• Also due to the nature of its enchantment it is superior to the bag of holding in regards to the amount of weight it can hold and the size of objects that will fit into it, although both have an effective interior volume of 64 cubic feet.
• Living creatures put into it will only shrink if they choose to fail their savings throws or it unwilling, fail a DC 14 CON savings throw.
• Creatures can breathe normally as long as the flap is open and in air. If the flap is closed they will run out of air in 10 minutes divided by the number of creatures.
• An anti-magic field will cause the backpack and everything in it to be restored to their actual size as long as they are in the field. A dispel magic cast at the backpack will do the same for 1d4 rounds.

Notes: Will weight <= 30 lbs, Utility, Container