It’s an odd, flat-grey metal coin with the image of a crone on one side and a triskele on the other.
When flipped, it transports the person using it to an area far above the place they were just standing. They appear to be standing on thin air looking over the landscape below. The only other thing the area contains is a desk, and sitting behind it is the crone pictured on the coin (in some universes, this woman is the personification of female deities associated with luck, chance, and fate). The borders of the area are shrouded with a thick fog which, if attempted to be traversed, simply transports the character to the opposite side of the area they walked in to, like a loop.
If it is a first-time visit, the crone will explain that they may draw from her tarot deck and change their fate. She will allow them to travel back to the ground, coin unused. After the first visit if the person flips the coin, they must draw from the deck or wait around for eternity to end.
The coins were created by the crone and scattered around the world. When a coin vanishes from a person’s inventory, it re-appears to the next neediest person. Sometimes the coins will get lost and mixed in with loot in dungeons, so it’s quite possible to find one in a chest.
If they appear spontaneously, it’s typically only to people in dire straits.