From Destinypedia, the Destiny wiki
Psion Operants are groups of powerful Psion, that originally belonged to the Cabal scout Legions stationed on Mars during the first game. They are tasked as Elite Psion units and are mostly seen as Majors in harder variations of missions, in the Scablands in a "eliminate the target" Public Event, Patrolling the Dreadnaught and uniquely designed variations encountered in the Dust Palace Strike.
Psion Operants function similarly to normal Psions except with higher durability, more frequent use of their Psionic Blast ability, and a higher chance of wielding high caliber Cabal weaponry such as Projection Rifles. Psion Operants also tend to be more aggressive, rushing down the opponent to melee them, or get a good line of sight to blast them with their Psionic Blast. Arc and Solar Psion Operants have Absorption Shields of their element instead of void when the Epic modifier is active.
List of appearances