Permanent Illusion--how to counter

[taliesin15]

Let's say there's a Permanent Illusion generated by a high level Illusionist Wizard, and it is something that has become a sort of prominent feature of a dungeon milieu. The entire area radiates magic, how do you suppose PCs can combat this phenomenom. Let's also say its a sort of life and death situation that they must resolve. I just want to make sure I haven't forgotten something. Not like I'm trying to kill off the characters. Sorry to be coy about the details, I'm just afraid one of them is lurking and I'd prefer them to solve the puzzle with their wits.

 

[FireLance]

Note that permanent image allows a Will saving throw to recognize it as an illusion if it is interacted with. A lucky roll could reveal the deception.