[quote=@Lord Orgasmo]

Or, depending on how much magic you like, maybe there's some weird planar influence and the tavern just so happened to get sucked into a different plane, and now you have to find your way back?

There's the old fashioned "barkeep was an evil wizard who works for a demon" approach and you guys were meant to be sacrifices, but the spell sent the whole ass tavern and now you're in hell, and you have to survive there.

There's endless possibilities. Maybe don't have a plan and fly by the seat of your pants. Your players can't know what you're planning If you don't have a plan.
[/quote]

The barkeep is Vecna. Nobody can see it. And I typo'd by writing a mage twice! I was thinking using a hag!

I could use my current PC from other campaign as an NPC here as an agent sent here to investigate. Perhaps the tavern has already vanished, and the players arrive after the incident.