I like the idea that the magic is tied to the jar itself. It leaves the implication that the cloud is trapped inside somehow. Maybe it's a nascent air elemental, just about to acheive consciousness? Go to Comment
I'd leave that up for the DM of course :) And yes, one could omit the safeties such as being usable only outdoors and not being able to enclose things in rock-strong cloud. Then they become dangerous indeed.
I like this and am actually seeing a potential of twisting it slightly to make it a dark cloud to add to my game. The flavor of it will fit into the campaign easily. Something the villain is going to use to darken the sky and/or hide his fortress on the mountaintop by placing a cloud around the peak so his castle can't be seen from the base of the mountain. Go to Comment
It also reminds me of this meta trend in children's books where they ask you to physically interact with the book like its images are real. "Don't Push the Button," "This Book Just Ate My Dog!," "We Are In a Book!," etc. Go to Comment
The PCs encounter an elaborate trap room, designed to fill with water, drowning those inside. Clever and resourceful, they disable the trap and move on.
Only later do they discover that this room is part of the elaborate cooling system that prevents beasts of elemental fire from overrunning the complex. While the fiery beasts run rampant, they begin setting fires, which causes the complex to become increasingly hot and smoke-filled. Additionally, the PCs now have to fight their way out past aggressive fire creatures...