Maestro's ring
From Tardis Wiki, the free Doctor Who reference
Maestro's ring was an ornate ring with a black stone, worn by the member of the Pantheon known as Maestro.
They used it to express some of their power, striking their tuning fork against it to create a supernatural resonance through which they could track down individuals in their vicinity. Notably, Maestro's father the Toymaker (TV: The Devil's Chord [+]Loading...["The Devil's Chord (TV story)"]) also wielded a ring of power by several accounts. (PROSE: The Celestial Toymaker [+]Loading...["The Celestial Toymaker (novelisation)"], Divided Loyalties [+]Loading...["Divided Loyalties (novel)"])