Demon Eye

The Demon Eye is a common flying enemy which spawns at night, and is usually one of the first enemies encountered. It moves in an arc-like pattern, ricocheting off of walls, and will be knocked back when hit by anything. It will follow a player until it is killed, the player moves too far off screen, or the player dies.

When killed a Demon Eye will commonly drop a lens. If your mana is not at full capacity it'll also occasionally drop a Mana Crystal.

Related to Eye of Cthulhu (boss) and Servant of Cthulhu. Demon Eye Hit By A Fallen Star