'Add Your Own Fluff' Cursed Item: Helm of Spying

What it seems to be: A helm that, when put, activates whatever spell is used to spy on others in your game system of choice. It works for anyone, not just spellcasters.

What it actually is: It does work as previously mentioned but for one important detail; The helm itself is not really magic, rather a magical spirit resides within it, a spirit that can read the mind of its wearer (no save allowed) and relishes in feelings of betrayal. If the helm wearer uses the helm to spy on someone they trust and/or care about, the helm will show something that is not actually happening that will lead the helm wearer to believe the other person is betraying them.
  For example, if a helm wearer uses it to check on his wife, the helm might show her cheating on him with a trusted friend or even an enemy of his. If he uses it to check on an ally, he might see that ally selling information to an adversary.
  In the same vein, if a trusted person actually IS betraying the helm wearer, the spirit will give a vision of the person acting in a completely trustworthy way.