Silver Crest

Prison, after the Jail Key door and the drop: down the stairs on the right to a chest. Fandom: shortly after the first Blob past the spiral staircase.

One of the 2 pieces for the round indentation at the top of the area; with the Gold Crest it opens the way to the Maze.

Spend your ammo before placing the 2 crests: doing so strips all your equipment (see the Gold Crest).