Bag of devouring
Essentially a bottomless pit in a bag, this bag appears to be a normal sack, like a bag of holding, and seems to be a bag of holding on closer inspection. However, the bag is a lure used by an
extradimensional creature; it is one of its feeding orifices. Issue 271 of
Dragon[1] featured an article titled "The Ecology of a Bag of Devouring" that discussed the nature of such a creature.
Any substance of animal or vegetable matter put into the bag has a chance of being swallowed over time. Even a person reaching in to retrieve or place an item, after the initial time, has a chance of being completely dragged into the bag and swallowed. The bag of devouring will act as a bag of holding, but every hour it has an increasing chance of swallowing the contents. Any plants or animals swallowed by the bag in this way are transported to the creature's stomach, digested, and lost forever, while inedible items are swallowed and spat into another plane.