From Destinypedia, the Destiny wiki
While the lesser Hive monsters carry out the Hive's will through overwhelming force, the Wizards plan the Hive's conquests and carry out the unspeakable rituals that create its menagerie of abominations.  In addition to fueling the Hive's might through sorcery, the Wizards also serve as its reproductive caste. A Wizard becomes fertile either from a mate or on her own, whereupon she will produce the pupae that give rise to the Hive's legions of Thralls.  In Destiny 2, Wizards gain a new look as well, appearing to have more armor on their bodies, and sporting a helmet with two glowing lines on either side of their helmets. They can possibly cast illusions upon others as well.
Wizards are often frustrating opponents on the battlefield, being able to unleash long range darkness blasts in rapid succession while swiftly flying around. The higher the Wizard is ranked, the faster they fire them. In addition, they can plant down poison clouds that deal damage over time, blur the player's vision, and slow them down. The vast majority of wizards come with Solar shields, except for Omnigul, who comes with an Arc shield. But once the shield of any Wizard is picked apart through concentrated fire, their defenses are effectively shut down, leaving them fully vulnerable to Guardian attacks.
List of appearances