You plunge the key into the barrier and watch as waves of barely visible bluish light run up and down along it

You plunge the key into the barrier and watch as waves of barely visible bluish light run up and down along it. It appears that a protective spell of some sort was hiding its true nature, but now it disappeared. An ethereal whisper comes from the door, and distinctly pronounces the word 'phylactery'. You barely have time consider its meaning when the key dissolves in the waves of blue light. "It's part of a plan. The imprisoned one can be free, but only by sacrificing the essence of his power."