It is absolutely the D&D equivalent of the run out of Moria.
The 1st level characters, investigating an ancient vault that was recently found with its door open, have entered to see what is within and seal the door. In gaining the key to seal the door, they awoke an Aspect of Orcus, left here ages ago.
Maybe they find a Paladin of the Raven Queen, killed in battle against a ghoul who had opened the vault in order to awaken the Aspect. That way it wasn’t their folly that woke the beast up. But in order to lock the door, they need to take the key off of the statue of the Raven Queen that keeps the beast asleep.
It is a skill challenge to get the eff out of there before the Aspect, with two rooms at the end that they must fight through. Every skill challenge the lose means an encounter that could very well slow them down and put the Aspect in front of them.
Thanks to Thor for the idea!