Gray Merchant’s Gold Coin

Wondrous item, common (requires attunement)

These coins drop continuously from the Gray Merchant’s bag, forming a trail marking where he has passed. They aren’t available for trade but can be freely picked up by anyone who comes upon them. Gold is abundant in the Underworld and considered worthless by the Returned, but even so, this isn’t a true gold coin. The coin vanishes after three days unless you attune to it, which causes it to persist for the duration of the attunement. You may use a bonus action to focus on the coin to determine the general location of the Gray Merchant. If the Gray Merchant is far away, you know the name of the area. If he’s nearby, you know his general direction. Whenever you pay less than the recommended price of an item in a trade with the Gray Merchant, you must roll a d2. If you roll a 1, you lose attunement to the coin, are unable to attune to any such coin for five days, and any such coins you touch vanish instantly.

Source: The Gray Merchant of Asphodel