Mechanical Eye

The Mechanical Eye is used to summon The Twins, the advanced and Hardmode version of the Eye of Cthulhu. It can only be used at night, which means consuming this item during day will not spawn The Twins. Using another Mechanical Eye while the The Twins are active will not cause any additional effects, and will not be consumed. If you have not defeated The Twins yet and are already in Hardmode, all enemies (with the exception of statue-spawned enemies and Meteor Heads) have a 1/2500 (0.04%) chance of dropping this item.

Achievement
you can get this as early as Eye of cthulhu or king slime

Trivia

 * The Mechanical Eye is the only mechanical item with no visible winder.

History
Œil Mécanique 기계식 눈