I'm running a homebrew dark fantasy play-by-post game, which is highly narrative-driven.
As such, the players were given plenty of freedom designing their characters and abilities. One of the players asked to have magic-detecting abilities. It seemed a little overpowered to me, but I felt we could all manage with it, so I allowed it.
The problem is that this ability is beginning to pose difficulties on the plot. The magical McGuffin can't really be hidden from the character. The evil wizard can't sneak up on the team. Magical traps are standing in plain sight. The list goes on.
I should have foreseen these issues, but didn't. I don't see a way to just take back his powers, not without upsetting the player and breaking the immersion.
Any way to back out of the situation gracefully, or should I just eat my own stew, throw out my old grand schemes, and make new ones?
Magic is cast via magical artifacts and the ability in question senses the presence of any magical item within a very wide radius, and - unless the magic is too complicated - determine what the magic is.