Wisp in a Bottle

The Wisp in a Bottle summons a wisp, a floating ghostly skull, to provide light. It serves the same purpose as the Shadow Orb or the Fairy Bell, but the Wisp not only keeps pace with the player, it actually moves ahead in the direction the player is moving. This can be used to see a short distance through walls. It cannot be used together with the Shadow Orb or the Fairy Bell, and summoning either will dismiss the other. The Wisp in a Bottle can rarely be dropped from Blue Armored Bones, Hell Armored Bones, and Rusty Armored Bones.

Trivia

 * This item might be a reference to the series of games : The Legends of Zelda (particularly Ocarina of Times, when Link is adult), where you can capture ghosts with empty bottles, and sold or use them later.