Phantom

Phantoms are flying undead hostile mobs in Minecraft that spawn in the night sky when a player has not slept in a bed or died for three or more in-game days. They typically appear in groups of three and attack by diving at the player to bite them. The spawning mechanics for phantoms differ between the Java and Bedrock editions, but they generally spawn above the player after a certain amount of time without rest. Phantoms serve as a penalty for players who don't sleep, encouraging regular rest periods. As undead mobs, they are harmed by the Instant Health effect, healed by the Instant Damage effect, and burn in sunlight. When killed, phantoms drop phantom membranes, which are used to repair elytra and brew potions of slow falling.