This trap is a clever concoction that will neither detect as a trap and in a sense does not use magic to kill the PCs. The PCs use magic to kill themselves in the end.
Wherever the DM sees fit the party finds a door. It is unlocked and not trapped. Upon entering the room they will notice it is the size of a large royal closet 10’x10′ surrounded by complex ceramic tile, perhaps shelving with odds and ends. Upon closer inspection (search DC 15) reveals multiple small holes in the walls and ceiling within the tile, about 50 in all. On the floor or one of the shelves lie 3 liquid filled bottles. Each bottle appears to have the same liquid, milky white with a scent of aloe. Each are potions of Gaseous Form. The potions last for about 2 minutes and have one dose each. One of the 50 holes is an escape rout to anyplace of the DM’s choice for their villain to get away. The other 49 just twist and turn to dead ends.
The unfortunate part for the PCs is that any player foolish enough to drink the potion and explore a false exit hole will not have enough time to come back to the room before the potion’s duration expires, thus a compressed adventurer.
Note: A DM could use this as an escape rout for a fleeing villain or a simple trap to deceive the PCs. As an added extra effect you should take the affected PC out of the room and detail his dilemma. Upon your return to the table you could describe the blood squirt that comes out of the explored hole.