This is one of the most effective trick/traps I've used in my games. It can be dynamic and very effectively create tension. I’ve used the bag on a stick a dozen times, and the results have always been excellent.
The bag on a stick can be placed anywhere: in a dungeon corridor, the mouth of a cave, in a nook or torch sconce, in an alley, abandoned building or sewer, blocking a footpath, on a dock pole or tree limb, or just beyond the campsite when the heroes awaken. The best part is that it can be used repeatedly, especially during the same adventure, and conceal just about anything.
If used correctly, this gag builds suspense and can buy enemies time, very useful with setting an ambush. The chance that something useful or valuable might be destroyed ensures that the heroes don’t just hit the bag with a spell from a distance (it can even be dangerous, see below). The following are suggestions. Combinations and new ideas are welcome and encouraged.
- The severed/shrunken head or appendage of an ally or mutual enemy. Potentially this head or limb might animate, speak, point menacingly, draw a message or cryptic warning, cry out in pain, spew toxic gas or spores, and so on. The mouth might barely conceal a skeleton key, message, or magic scroll. It might also be a poisonous centipede.
- A purse of coins or other treasure from a mysterious benefactor with their own agenda. Alternatively, this could be some clue, a map fragment, or some other information.
- A huge hornet nest, a coiled asp, or other springing or spitting creature. For tougher parties, a caged quasit in raven form. Useable as a trick/trap or guardian (see #6 below).
- A decanter filled with fresh water, excellent brandy, vaporous plant killer, volatile naphtha, unholy water, a magic potion, or a pheromone sprayer. This vessel might also act as a counterweight, sprung once it is moved (see #5 below).
- A signal, a shattering bottle, bundle of ignited smoke sticks, noisemaker, or whistling projectile, maybe tied to a powerful monster or a hatch freeing a trapped stirge swarm.
- The release for a hooked net with bells, or a tumble into a pit tomb sacred to natives, or a secret stairwell. Maybe the handle was broken and the bag now serves as a makeshift grip that triggers it when pulled off. Alternatively, the “stick” is a removable key or magic rod that serves multiple functions, possibly acting as a heraldic device recognized by intelligent denizens and monsters of the dungeon.
- A pungent plant or a piece of meat infested with a swarm of biting deer flies. Perhaps the smell attracts nearby predators or buzzards that mark the spot from the sky.
- A cursed magic item or demon skull with knowledge of the area but far too much to say, and/or its own agenda. The ‘stick’ might also be a dancing staff or broom covered in adhesive glue.
- A Helm of Alignment Change to place an enemy or spy in the party, or one that switches race or gender, or makes the wearer berserk, or polymorphs them into a monster. This helm might also make the wearer incorporeal to be snatched or to witness some transplanar event.
- Idol of Discord, or Fascination. Those who fail their save will want to possess it, even fighting allies to do so. It may speak to them, tell half-truths of buried treasure or an escape route to gain their trust and get worse as time goes on.
- A crystal ball. While the adventurers fret, scry, or dally, a patrol or random monsters are bound to pass by. Removing the hefty crystal ball sets off a trap, or starts a gearbox turning, locks all doors, or exposes a deadly sigil beneath.
- The ‘stick’ is the handle of a lawful evil sword or mace. It renders powers and offers advice to its wielder, so it can attempt to seize control later and rebuild a once-great multiracial kingdom.
If you use the bag on a stick right, your players will curse you but they'll never forget it.