Knapsack of holding (Little)

Knapsack of holding.
In addition to its normal compartment, this bag can connect to a pocket space with 15 inventory slots. To access its inventory, just place your hand at the mouth of the Knapsack and concentrate on it. Any item that can fit through the mouth of the Knapsack can be stored. As long as the pocket space is in use, the Knapsack can not be stored in your inventory, If this bag is turned inside out or damaged beyond repair, all items stored magically will be ejected.

Reference
Acquired in Chapter 11 "Unpleasant introduction"