Crab, Duffel 2014

Uses an extra-dimensional space such as a bag of holding as its “shell.” Bag can hold creatures in addition to the crab based on extradimensional space's size. Breathing creatures inside bag can survive up to a number of min equal to 10 divided by the number of creatures (minimum 1 min) after which time they begin to suffocate. If bag is overloaded pierced or torn it ruptures and is destroyed. While this would normally cause the contents to be lost in the Astral Plane crab’s half-in half-out existence kept the bag constantly open even when it fully withdrew altering the bag which simply spills out its contents into area when the bag is destroyed or crab dies. Bag becomes a standard bag of holding or similar magic item with extradimensional space 24 hrs after crab dies.

While motionless indistinguishable from its extradimensional bag with an ajar lid or opening.