Source: Princes of the Apocalypse

Wondrous item, uncommon

This backpack contains the spirit of an air elemental and a compact leather balloon. While you’re wearing the backpack, you can deploy the balloon as an action and gain the effect of the Levitate spell for 10 minutes, targeting yourself and requiring no concentration. Alternatively, you can use a reaction to deploy the balloon when you’re falling and gain the effect of the Feather Fall spell for yourself.

When either spell ends, the balloon slowly deflates as the elemental spirit escapes and returns to the Elemental Plane of Air. As the balloon deflates, you descend gently toward the ground for up to 60 feet. If you are still in the air at the end of this distance, you fall if you have no other means of staying aloft.

After the spirit departs, the backpack’s property is unusable unless the backpack is recharged for 1 hour in an elemental air node, which binds another spirit to the backpack.