Sheer Trail Gap
The only one way forward on this ledge is across a 25 foot gap.
Fly Away. The use of fly or similar magic triggers a critical success for that adventurer.
Lava. Lava—and almost certain death—waits at the bottom of the gap.
Sheer Ledge. Checks made to jump across the gap or climb the angled wall beside it have disadvantage .
A group Athletics check can be made to climb along the wall without disadvantage if at least one set of climbing gear is used, and only a group Engineering check can be made to create temporary supports in 16 (4d4+6) minutes.
Critical Failure: The adventurers plummet 2,000 feet down into the volcano. As the fall begins each PC makes a Dexterity saving throw to catch a handhold on the wall, but otherwise thermal updrafts slow their descent and they have 5 rounds before they hit the bottom, taking 70 (20d6) bludgeoning damage on impact and landing in lava.
Failure: As a critical failure, but adventurers have advantage on their Dexterity saving throw to catch themselves.
Success: The adventurers pass over the gap without mortal consequence.
Critical Success: Passing over the gap proves to be easier than expected and everyone in the party gains inspiration.