D&D 5E PotA - Going back to a dungeon

[abirdcall]

I'm currently running PotA.

The party explored the air dungeon/temple but retreated before confronting the prophet.

They are planning to go back next session. What are some new challenges they could face?

 

[Eltab]

• An Invisible Assassin (whatever the air elemental sneak attacker is called).
• Traps that use Gust of Wind to slow the party or maybe blow them back towards a cliff.
• Perma-Cloudkill in a low area, so it won't flow away
• A couple of minions with a half-dozen Seeker Darts. They let the party see them then hide. When the party goes past (a good long safe distance), they throw the darts from behind the party's backs and around a few corners.
• Wall of Wind someplace they kicked down a door.
• Prestidigitation "bad odor" someplace the cultists want the party to stay away from
• Swarm of bats or ravens. Trained hawk / owl / eagle to mess with a Wizard's familiar (if any).
• A Griffon-Rider of Waterdeep is searching for Lady Belabranta. He has a crush on her and wants to rescue her from whatever monsters ruined this fortress.