Key

After a few rooms, Isaac came upon a room which was empty except a gray chest which stood in the center. He touched the top and it flung itself open, shooting out its contents in every direction. The items included were two bombs, which he promptly added to the backpack he had found, a coin, and a key. He hadn't seen a key like this before. It seemed to glow silver in the light which emanated strangely from the ceiling. He put it in its own pocket and continued on his way to the next room. What a lucky find.