Ring the Bell
While you are enjoying a meal or drink, Sal moves to a bell hanging from the wall behind the bar. He grabs the clapper pull and rings it loudly. A party of four adventurers stands at the bottom of the stairs and with the ringing of the bell, begins climbing the stairs until they stand before the large, ornate double doors. Sal makes his way from behind the bar to join them. Other people move to watch, some climbing the stairs to the first landing or the left side balcony to get a better view. Many remain at their tables but watch with interest. A few climb further up the stairs, some even standing on the center balcony.
Sal asks the party for their coins and inserts them one at a time into a slot on the doors. Each coin clinks as it falls and once all the coins have been inserted, Sal grabs the large handles and pulls, opening the doors. Looking through the open doorway reveals a mirror of the balcony and the inn common room. As the party begins to move toward the opening, a figure bursts past them, darting for the open doorway with a desperate cry.
In a flat, monotone Sal says "No, wait, don't." and seems otherwise unconcerned.
The moment the figure breaks the plane of the doorway, they pitch forward as if struck a heavy blow, slamming face down onto what now appears to be a rough stone floor. The other tavern, visible through the open door, has become dim and hazy. Darkness presses in from the edges of the doorway and what can be seen beyond suddenly resembles a dark cavern. The figure lies motionless at first, then weakly stirs, blood running from a broken nose. Something else moves in the darkness. A huge shape partially emerges from the shadows. A fleshy, ropelike, tendril slaps down onto the figure on the ground. A multitude of hands, disturbingly humanoid in appearance, sprout from the tendril, reaching, grasping. Tubular proboscis also burst from the trunk of the tendril, slithering to find purchase in the flesh of the now frantically struggling person. Then the screaming begins. As you watch the fleshy bulk begins to drag its prize into the darkness. Several of the protuberances that had not yet attached themselves to their victim, writhe and pop with a fleshy squelch, transforming into mouths with misshapen teeth and tongues. The mouths open wide in screams of their own, mimicking those of the doomed transgressor.
Eventually, the darkness recedes. The screams, now more incoherent gurgles and mewlings fade. Soon, all is as it was. The door remains open and a warm and inviting tavern can be seen beyond. People sit at table, talking, laughing, seemingly oblivious to what you have witnessed.
Sal speaks simply to those gathered, "Please don't try to go through the doorway unless you have first given me your coin."
The party looks to each other nervously, but after a moment's pause, they proceed into the other inn.