I have designed this spell:
8th level divination
Casting Time: 1 minute
Components: S M (an earwig or a hollowed out animal horn)
Duration: 1 hour, concentration
Classes: Bard, Wizard, Warlock, Sorcerer
For the next hour, you listen very closely for the sound of your name. If any creature on the same plane as you uses your name to refer to you, you are able to eavesdrop on their conversation. For one minute, you can hear what takes place as if your ears are in the room. If another creature on the same plane as you uses your name to refer to you within the hour, you can choose to turn your attention to that one, or continue listening to the current one.
I currently have it listed as 8th level. Is this appropriate? On one hand, there is no save, and no way to detect that it is happening. It has no limit on how far the spell reaches. However on the other hand, it only lets you hear, not see, it can be blocked by Nondetection, and if your enemies find out you use this spell, they can simply stop using your name to refer to you.
Some changes I am considering:
- Duration: 8 hours concentration instead of 1 hour
- Duration of eavesdropping 5 minutes instead of 1 minute
- Text that specifies that you feel momentary sharp pain in your ears when you key in. Maybe it could even deal 1 psychic damage?
- An invisible ear-shaped sensor that could be detected