building trap/puzzle room help

[Thac0 Redeye]

Hello all,
I am creating a one shot puzzle dungeon. They have to collect a key in each room to open the vault in center that takes multiple keys.
this room is round with a center pillar that is very similar to the power stone vault in the beginning of "Guardians of the Galaxy", with the key floating in the light instead of the power stone sphere. The light force field will stop any non living attempt to get the key. There will be 6-7 shorter pillars surrounding the center each about 4' high with a single lever on top of each. Each lever does something different. None release the key. All the chara's have to do is reach in and grab the key. the forcefield will stop any other attempt from getting the key. it it will block undead, mage hand, etc. and dismiss any summoned creature.
What I would like is help coming up with effects for the levers. Here's what I have so far.

- fireball Ref Half
-chain lightning Ref Half
-poison cloud Fort Neg
-turn to stone Fort Neg

This is a one shot to get the chara's up a few levels before we start the big adventure. So please no effect that will send party on wild goose chase.

Thanks

[Telonius]

Maybe not the most creative solution, but 6-7 pillars is just the right number for a prismatic effect. (Substitute "start of the dungeon" for "another plane")