Faultline Coronet

A dull grey iron coronet circles the brow, split by one impossibly fine crack that runs around the entire band without ever widening. Underground, the fracture gives off the faintest pale glow, and the wearer sometimes feels distant chambers through it as a pressure behind the eyes.

While the wearer is underground, they see every open space, void, and worked passage within 60 feet through solid rock, and what lies buried in it. Above ground the coronet shows nothing, though the wearer can still tell worked stone from natural at a touch and knows how thick a wall is by knocking on it.