Lens

Lenses are an uncommon drop from Demon Eyes. However, they are not dropped by their Hardmode counterpart, the Wandering Eye.

Another form of lens, called the Black Lens, can be used to craft Sunglasses. Black Lenses have a much lower drop rate than the standard Lenses.

Making money
A much better way to get money from lens, is to craft a Suspicious Looking Eye, killing the Eye of Cthulhu and selling the reward.

History
Lentille