Use headology. That is, use the normal way of thinking to completely trick and kill adventurers. Like an easily spotted pit trap. And then another. And another, except where you'd stand to avoid it, like the other two is actually trapped on the third one. In between, have some sort of mundane arrow trap just to keep them from thinking about it too much.
The dark and the unknown are the things people are most afraid of. Do not underestimate the power of lanterns lighting on their own, and then, at just the right moment, snuffing out completely, with soft laughter in the dark. Even before anything real happens this will freak people out. Set up a detect life spell that turns on the lights, and another at the end of the hall that turns it off. Permanency should do it. At this point, have a door open. Tell them they can leave now. Do a count-down.
Also, find ways to deplete spells and use auto reset traps. Hire talented artists. They are worth the gold. By the time they get to the real encounter, they won't trust what they see, so they might not strike and some will die. Or you can make some, but not all the encounters real. Mix things up--make some things magical and others totally mechanical.
Never use the same thing twice. Or do, just to set up an expectation that will be completely wrong.
Make sure that avoiding one trap just leads you into another...Throw in some necromancy and it's just good, dark fun. Any trap with a zombie is a good one--so, one could be, you avoid a mech trap, but a zombie is set to grab one person out from a wall (or do an upgrade so the undead has a good grapple). Make it a ledge so the choices are: die in a trap or come to zombie. Anyone trying to help would not have much room to maneuver and help would be limited by whoever happens to be next to him. If it works well, it's a surprise attack, they are grabbed and pulled in, never to be seen again. If you can pipe in his screams, so much the better....
Edit: And since you are looking to trap magic users, have things triggered by the use of certain spells, like, oh say FLY. Basically, think like the adventurers. If you had their spells, what would you use to counter? Have a healing orison trigger a poison dart/ arrows that seeks the center of it. Make sure that whatever they end up using has a nasty consequence.