Appearance and Mechanics Edit
It's unknown why Ewan made the trinket, though it's likely he did so as a failsafe in case his creations ever became a danger to himself and/or others. Smart.
The trinket was given to the Fairytale Detective by Ewan after the Detective freed him from the Automaton Queen's captivity. The Detective used the trinket to destroy an Automaton Soldier and, later, Queen Valla and her Golden Bears.