Phantom

The unnamed Mob B, also known as the Monster of the Night Skies, is a flying Hostile Mob set to be added in the upcoming Update Aquatic.

Spawning
This Mob will spawn in groups at a high altitude. The number in a group is as yet unknown.

Offense
Mob B will attack by swooping down to bite the Player. According to information released so far, it will be attracted to Players with "insomnia"—those who haven’t slept in many Minecraft days.

Trivia

 * Mob B was the second choice, and subsequent winner, of a Minecon Earth poll where fans of Minecraft could choose which new Mob of four they wanted added to the game.
 * Mob B resembles and seems to have been based of off a manta ray, an aquatic creature.
 * This will be the first naturally spawning hostile flying Mob.
 * Vexes are flying hostile Mobs, but they only spawn when summoned by an Evoker.