Mimics

The Mimic is an aggressive Hardmode enemy disguised as a Chest, appearing as the appropriate Chest type for the environment. Mimics will look exactly like Chests until approached, at which point they will chase the player.

Mimics take on the appearance of Chests that would normally be found in a given area: normal brown chests closer to the surface, gold chests found underground, an Ice Chest in a Snow biome, and locked Shadow chests in The Underworld.

Mimics are immune to the Cursed Inferno and Confused debuffs.

Mimics can be spawned by the player using the Chest Statue, but they will not drop any coins or items this way except a Mimic banner.

Only Mimics stylized after an Ice Chest will drop snow biome Mimic drops, such as Frostbrand and Toy Sled

Identifying

 * Using a Hunter Potion will make Mimics glow like any other enemy.
 * Using a Spelunker Potion will not make Mimics glow like real Chests.
 * Mimics disguised as Gold Chests or Shadow Chests will not sparkle as the real versions do.
 * If a new Chest appears at any point in an area you know well, it is probably a Mimic. Naturally-occurring Chests are only placed at World creation.
 * Mimics can sometimes be identified by the fact they do not always perfectly fit the tile 'grid', and thus do not line up perfectly with blocks, as normal Chests would.
 * Real Chests will never be situated directly over any empty tile spaces, so if you see a Chest on top of any empty tiles (including those resulting from sloped land), it is a Mimic.
 * Real Chests will never spawn on top of other background objects, such as Life Crystals, since real chests are background objects themselves.
 * Shooting a stationary disguised Mimic with a ranged attack will cause it to become active and start chasing the player. Suspicious-looking Chests can therefore be tested from a safe distance by firing at them.
 * Real chests will show up on the map, mimics however will not.
 * Occasionally, Ice Chest Mimics will spawn on breakable ice, like over water. A normal chest can only spawn on solid land
 * Rarely, Mimics will have slightly thicker outlines than a normal chest

Trivia

 * Mimics first appeared in Dungeons & Dragons in 1977, and have appeared in countless RPGs since.
 * Chest statues, which spawn mimics are sometimes generated on top of wires connected to a pressure plate from a trap. This can result in a mimic attacking and killing you early on in the game.