From Destinypedia, the Destiny wiki
Servitors' primary usage in combat is to support accompanying Fallen units by emitting a purple glow, giving them a nourishing boost. They are shown to be a resilient threat and are capable of firing powerful blasts of Void energy from their eye, which is also a weak spot. They frequently try to protect this weak spot when in combat, making them difficult targets. To evade incoming attacks and flank their targets, Servitors will occasionally teleport short distances. In Destiny 2, Servitors serving under the new Fallen House of Dusk are given the ability to fully shield nearby Fallen units, granting them complete immunity to incoming damage. The Prime Ether Servitor in the Ether Resupply Public Event also has two new abilities, called Servitor's Grasp and Servitor's Fall. The Grasp teleports Guardians away from it, while the Fall sends them high up in the air. Ironically enough, they are also seen to be missing much of the black shielding near their eye and around their back, which may be attributed to the desperation found in the new House.
There are more powerful Servitors known as High Servitors. Above High Servitors are Prime Servitors, the highest form of Servitor known. Prime Servitors take the place of a god among the Fallen, as they also produce multiple Servitors and major tons of Ether. With this, each Fallen House having their own Prime Servitor. Certain Servitors function as pilots, and are called Pilot Servitors.
Apart from supporting Fallen in battle, Servitors process matter and energy into Ether for the Fallen's sustenance, and anchor comms and provide technological acuity. They also serve as navigation aids for Fallen Ketches, and possibly Skiffs. Some Servitors also serve as personal support and ship pilots for High-ranking Fallen.
List of appearances