So we create a spell trap, that casts Find Traps on people, and casts Phantasmal Traps, and finally have a magic mouth trap that casts suggestion on anything that comes in, and makes people believe that every time they spring a trap an innocent creature is killed. So everyone that finds this spell trap knows inexplicably that there is at least one trap in the room. Have many many fake traps all over, and several real ones. Put this in a labyrinth. make the wrong way be "less" trapped, but have the actual traps activate once they reach the dead end. So they know with definite proof that there are traps on the way back, that dont seem to have done anything, but if they failed their save seems to have killed many innocents whenever triggered. And have them dodging real traps the whole time. Add in some Trap Haunts (ghosts that possess traps) and maybe a fiend of possession or twelve that possess the traps. Make it so that the group absolutely hates traps by the time they make it out of this. And for the finale, a resetting Dimension Door trap that teleports people to the beginning of the dungeon, and one at the entrance that teleports people back in.