'We've all been wrong. It's not a key. Not a key at all. It's the lock!'
To a normal user, the pendant can be used to travel the nearest lay lines to the next thundershifter they triangulate with. It can take users awhile to figure out how to navigate - but the pendant also gives them an innate sense of navigation and location. Wearers in essence can never become lost.
To an advanced user, the pendant can actually channel the energy of nearby laylines. To what effect, I don't yet know.