A bracelet of 26 flat crystals,stone beads or maybe iron coins, each with a single letter of runic alphabet engraved on each face, or cast right through.
When you ask a question of the bracelet, it will brand the letters of response into the wrist of its wearer. (1d4-1 damage )
The wearer will need to unscramble the response, entertaining the possibility that it might require repeated letters.
It's a direct line to a demon. Maybe it is trapped in the bracelet, bound to answer truthfully until the bracelet is broken, releasing it. Once released, it only tells lies out of spite, but don't let the players know. It might not even let them live.