Quote Originally Posted by lperkins2 View Post
The idea I would use is to create an illusion of a mirror, it will fail if they walk close enough, since they will see themselves, but tucked into a corner, at a fair distance, it works really well.
Yeah, based on this and Potato_Priest's post, I can see where we'll differ on this.

I don't think an image of a mirror will show reflections. In the same way you would walk in front of a picture (which is just an image) of a mirror and not see your reflection, so too would a minor illusion (which is just an image) of a mirror not show your reflection.

I wouldn't even have thought that people are making reflective surfaces with this cantrip. I thought the trick was to make an image of the area behind you, not make an actual mirror.
The lines don't matter as much as you might think, since your eyes track to familiar shapes, and a mistake in the wall doesn't really qualify. Certainly if the guards are alert, it will stand out. Also is more likely to work outside or in a cave than in a proper dungeon.
A five foot patch of wall that doesn't change in any way as your perspective changes I think will be quite noticeable. Just imagine a 5x5 cardboard cut out and standing behind it. The angles where it would work are not many.
Mechanically, I would let it grant concealment sufficient to attempt to hide, possibly with advantage on the hide check if the conditions are good enough. I wouldn't treat it as equivalent to a stationary invisibility spell.
I can see it being tricky. I just have trouble seeing how it would make you invisible.