If one drink's the potion, perhaps they will see an image of the map...once i had a PC drink from a fountain of direction, and its effect was that the PC's eyes started to shine beams of bright light that allowed him to follow a hidden magic trail leading to a "lost shrine"
you can also have the bottle, once empty, shine a refracted map of light on anything it is reflected off of (a wall, floor etc)...after the potion is consumed, the etching could be appearent, and when held up to the eye to read it, the PC would find it backwards, and the other PC's would see the map shine on his face...
If one drink's the potion, perhaps they will see an image of the map...once i had a PC drink from a fountain of direction, and its effect was that the PC's eyes started to shine beams of bright light that allowed him to follow a hidden magic trail leading to a "lost shrine"
you can also have the bottle, once empty, shine a refracted map of light on anything it is reflected off of (a wall, floor etc)...after the potion is consumed, the etching could be appearent, and when held up to the eye to read it, the PC would find it backwards, and the other PC's would see the map shine on his face...