Magic Mirrors

The Magic Mirror is an item found in Chests in the Underground, Underground Jungle, Ocean, and Dungeon. It allows the user to warp back to their Spawn, with a roughly one second delay, at the cost of 20 Mana. If you have not set a Spawn point using the Bed, the Magic Mirror will teleport you to your original spawn point in the World.

The Mirror was created to discourage players from committing suicide as a method to return home; it allows players with low health to return home without the risk of losing their loot. It is useful if a player finds themselves overwhelmed by enemies, under deep water with little breath left, or as a quick means of escaping Chasms.

Note that using this item is functionally equivalent to using "Save and Exit", with the exception that items on the ground will not despawn when using the mirror, like exiting a world would.

Trivia

 * The Magic Mirror is a reference to the game Legend of Zelda: A Link to the Past, in which Link uses a magic mirror to return to the light world when in the dark world, or the first room of the dungeon he was in.
 * The Magic Mirror could also be a reference to Luigi's Mansion in which examining a mirror with the Game Boy Horror (first-person mode) will cause you to be teleported back to the first room in the game.