Unfortunately I had to be generic because I can't imagine it in my mind.
I guess it depends by the kind of trap. For example if your trap drops an explosion you can return the refs of those hit and cast a spell on them, but in that case you could simply use a custom explosion and increase the "power".
If the trap isn't supposed to have an explosion, but you still can drop it, you can drop an explosion with invisible mesh, as effect you will see the actors blowing away.
If the trap uses a projectile (i.e. the baseball trap), you could use an Object Effect and cast a spell when you hit your target.
You could drop a trigger zone (the orange primitives) around your trap, so that those inside the trigger are those potentially hit by the trap when it triggers.
etc.etc.
Would you describe a bit more your trap and how it works in game?