Super mutant overlord

Super mutant overlords are a type of Vault 87 super mutant. They are evolutionarily somewhere between super mutant masters and super mutant behemoths. Super mutant overlords only appear in the Fallout 3 add-on Broken Steel.

Four Super Mutant Overlords can be seen on Mothership Zeta, frozen in the Cryo Lab. They will remain frozen in their containers unless the player activates one or two switches which will awaken them. If awakened they will be unarmed, but will proceed to attack any aliens that may happen to be nearby, as well as the player and his allies. If killed, their bodies can be looted for Stimpaks as well as experience.

Characteristics
Normal:

Tri-beam Laser:

Super mutant overlords are some of the toughest enemies in Fallout 3, wielding powerful weapons and possessing 2.5 times as much health as a deathclaw or a sentry bot.

Weapons
Overlords carry gatling lasers, missile launchers, tri-beam laser rifles, and super sledges as standard weapons. In a rare case, you may find an Overlord with a minigun, assault rifles, AER9 laser rifle, or Chinese assault rifles. Sometimes, like in Germantown Police HQ, one may be found carrying a hunting rifle that they might not be actually capable of using, and so he'll just attack with his fists.

They are most commonly equipped with tri-beam laser rifles as ranged weapons. This can be problematic especially on higher difficulty levels since they inflict an extra 40 damage per shot. Even if you have 85% damage resistance, they can still knock off roughly 25% of your health (assuming you have nearly 600 hp), making overlords exceptionally deadly with this weapon.

Locations
Super mutant overlords can be encountered anywhere where regular super mutants appear usually at high levels, but can be found at low levels at some places, like outside the Citadel, Germantown Police HQ, and the Museum of Technology. Overlords can also spawn in Bailey's Crossroads, in Operation: Anchorage, the Cryo Lab in Mothership Zeta, and GNR Building Plaza. Overlords also become more common on the higher levels.

Appearances
Super mutant overlords appear only in the Fallout 3 add-on Broken Steel.

Bugs

 * Sometimes, when an Overlord is equipped with a Tri-beam Laser rifle, it'll stay in place, aiming at the player or quickly holstering/unholstering its weapon, but never shooting until killed.
 * During "Big Trouble in Big Town" is when this happens most often: Sometimes, Overlords and Masters (the only two confirmed) will appear as simply "Super Mutant". They still have the same Health and Characteristics as an Overlord/Master, however they may not have the usual Overlord/Master Inventory (They may have Dog/Ant Meat like a typical Super Mutant would). When this happens you may also notice that Overlords may not have their signature weapons, but instead they may possess a Hunting Rifle (Which cannot be equipped by Overlords therefore they will attack you with their fists while the rifle will hover over one of the fists) or a Chinese Assault Rifle (Overlords can wield it, though they only use one hand to fire it). This has also been confirmed with Super Mutant Masters.
 * They may freeze in one place while fighting and are incapable of attacking if they are not moved by explosives or melee attacks.