The Magic Mirror is an item that allows almost instant teleportation back to the player's spawnpoint. It can be found in Gold Chests located underground. The item has a short delay of about one second; during this time, the player is susceptible to damage.
Be careful: While in the hotbar, the Magic Mirror can be used accidentally while exploring or fighting. This can be avoided by keeping the item out of the hotbar or locking it.
Using a Magic Mirror while the "Horrified" debuff (which only happens naturally while fighting the Wall of Flesh) causes the player to explode, giving the unique death message "[player's name] tried to escape".
Simply exiting the world and reloading it can be used as a substitute for the Magic Mirror, though this has the downside of taking longer and causing all items which were on the ground to de-spawn.
Since teleporting with the Magic Mirror takes some time, you can still die while doing it.
The Magic Mirror does not send you back to your original spawn point. This means that it can be used to teleport to the Nurse (If you have your Bed in her room) for quick healing.
The particle effect of the Magic Mirror is similar to the Magic Missile's impact particle effect, where it lights up surfaces or enemies while the particles emit.
The item being a magic mirror may be a reference to the teleporting mirror in "Zelda: A Link to the Past" or "Luigi's Mansion".
Bugs and Glitches
If the mirror is used, but the player switches to another item before the particle effects dissipate, the item will spin around then disappear.
If the player loses connection to the host or leaves the game with the Horrified debuff, when the player comes back he/she will instantly die.
In the mobile version, when using the Magic Mirror there is no 1 second delay.