Monoeyes are enemies seen in the Kid Icarus series. They are red creatures with one big eye and tentacles. They are commonly described as "one-eyed ghostly plasmas".
Monoeyes are usually seen in groups of four, as they fly down from the top of the screen, hover around for a few seconds, then swoop down at Pit before flying off screen. They are relatively common, especially in the Underworld.
Kid Icarus: Uprising
Monoeyes are also in the long-awaited sequel, Kid Icarus: Uprising. In this game, Pit encounters them both in the sky and on the ground, where they not only float around, they also show projectiles from their eyes. Again, they are usually seen in groups.
Kid Icarus: Uprising - Idol Description
"A Monoeye is a surveillance drone in the Underworld Army. Though it is capable of draining life from its target with its tentacles, a lowly Monoeye will never do so on prey like Pit. He's just too divine to touch!"