Mimics take the achievement of opening a chest and turn it into a test. This first mimic in Sen's Fortress sits askew in the room, its chain uncoiled, and faintly heaves up and down as it breathes. More than that, it makes every future chest a possible threat.
Mimics have gangly arms that shoot out of the chest to grab their prey. Similarly, their long legs emerge from underneath to raise them so they tower over the victim. A mimic will gnaw on its captured prey with teeth composed of boney fingers and thrust the victim into the belly of the chest. It does all this while its tongue waggles out of its mouth, flailing in an upsetting way.
The mimic can be triggered without grabbing the Chosen Undead by hitting the chest before opening it, or it can be pacified with Lloyd's Talisman. Slaying it or pacifying it will produce the item the mimic was holding as a reward.