The backpack of holding is one of the most popular 5th edition D&D items. It’s a wondrous item that’s much larger on the inside than you might expect from its appearance. It’s actually roughly 2 feet wide at its mouth and 4 feet deep inside. The capacity comes from internal Hammerspace, so even a thoroughly packed Bag of Holding weighs no more than a regular bag would.
What’s more, because everything in it is in another dimension, the contents of a Bag of Holding can’t be found by spells like Locate Object and conversations held within them are safe against Scrying. Obviously, this makes it a fantastic tool for smuggling creatures and objects, but you can also use it to give players an advantage in combat or in difficult spaces.
For example, a halfling bard in leather armour should fit into a Bag of Holding with ease, but that goliath in full plate will not. You could also use the Bag of Holding to create a booby trap for your enemies. Fill the Bag with a flammable liquid or other dangerous substance, and when an unsuspecting enemy opens it they’ll find themselves in danger.
Despite its great utility, it’s important to remember that the Bag of Holding is still a dangerous item to have in your party. If it’s overloaded, pierced or torn it ruptures and its Contents are scattered across the Astral Plane. It’s also a good idea to make sure the Bag of Holding is always firmly strapped on before your characters enter a dungeon, and that it has a decent magical lock.