“During the Mimic Hunt, many chests in the game have a chance to become a mimic when someone tries to loot it. Once defeated, the Mimic gives you a Mimic Token in addition to the regular loot that would normally be in the chest. Any non-raid chest opened by a character level 3 or above can become a mimic! Even Champion chests can become mimics, and will reward Tokens in addition to Mysterious Remnants and regular loot. Every time a player finds a mimic chest, the chance for the next chest to be a mimic drops slightly, and every time a player doesn’t find a mimic, the chance goes up! Players can also purchase Mimic Bait in the DDO Store to guarantee that the next chest they loot will become a mimic!”
If mimics seriously creep you out and you think this is just the worst event ever, you can pick up Mimic Repellant, which’ll stop mimics from spawning. I googled for this and English has no Greek-ish sounding name for mimic-phobia. Come on internet, help me out here.