Lost Mine of Phandelver

Fairly predictably, You're standing on the cliffside of a tall mesa propped next to an even taller mesa. No way down, but there is a way forward. The taller mountain seems to have a cave opening with constructions that resemble a mineshaft. As you look in, you see a man who appears antsy, not being able to keep his head or hands in the right place for that long. He tells you his name is Phandelver and almost a whole of his Bag of Holding's supplies have gone missing in this mine and, based on his mannerisms, clearly can't go in there again. (if players choose to bring Phandelver into the mines, make him suspiciously aware of the traps encountered)   Therefore, it's up to you to find the

Lost Mine of Phandelver (Overview)

A dungeon dive! This is the one time to get materials that could be helpful later on. Story-wise, Phandelver wouldn't tell the difference between a bag of holding and a pouch with a shiny rock in it.  As for the dungeon, adventurers will find numerous traps and encounters based on air (The "Phan" in "Phandelver", don't tell them yet) that will either be obstacles or tools for traversing this gassy domain.