Sky is introduced in Kid Icarus: Zeus's Lightning Bolt. This female angel was sent to Pit by Hera, goddess of childbirth, women, and marriage and wife to Zeus. She is introduced early in the game, and attacks you when first seen, but then makes an alliance with Pit and Dark Pit.
Sky is the same age as Pit and Dark Pit. She is sensative yet aggresive sometimes in the game. Her signature weapons are the Sky Fans (Which are unlockable). She is the boss in the level you meet her.