They are clad in what appear to be hazmat suits, no one has ever heard them speak, and their ability to seemingly appear out of thin air and leave as abruptly as they have arrived has given rise to rumours that they might be supernatural beings.
What little is known about the Specters is derived from various sightings throughout the wasteland. Though not all witness accounts are reliable, seeing as witnesses are more often than not traumatised by the event and many are superstitious, it is generally agreed upon that their arrival coincides with thick fog moving into the area, and that they appear where people least expect it. Attempts to follow them after they leave again have never proven successful.
Though it is entirely unknown why they do what they do, when they arrive they search out a specific target settlement and wipe it out entirely. Their choice of objective varies erratically with no clear pattern to be recognised, as they have been known to assault farms, villages, Raider camps, trader outposts, and even old US military bases. When they do, however, they engage with deadly efficiency, being able to strike large settlements with a mere dozen units.
The first signalisation of the Specters was in 2223, when the former city of Cheyenne, Wyoming, at the time a large settlement that had almost reached the size of a Pre-War town, was suddenly turned into a ghost town when every single inhabitant was killed in a mysterious assault. They have since destroyed several other settlements, most importantly Boulder in 2232 and Fort Collins in 2241.
The Specters appear to have some form of caste system, as two distinct types have been distinguished. The first caste, dubbed the ranger caste, is the most common of the two by far. They are clad in full-body hazard protection suits, with light combat armour over it. The ranger caste comprises the organisation's regulars as well as their snipers, and they are equipped with either semi-automatic carbine rifles or scoped sniper rifles.The second caste is the sentinel caste. These Specters are seen even more rarely than their ranger cousins, and only seem to be involved in the largest operations. They are more heavily equipped; the hazard suits are complemented by a metal helmet and a gas mask with a red visor, and some of them carry backpacks. They wield automatic assault rifles and light machine guns, further supporting the theory that they are only involved in large-scale assaults.
Despite their obvious military nature, they do not appear to have any semblance of rank structure or hierarchy, as they always operate in perfect unison and coordination. It appears they all collectively know what to do, almost like a form of hive mind.
Specters all wear a dark grey hazard protection suit, sporting a light cuirass over it to protect their vitals. The cuirass also sports spare ammunition cartridges. Sentinels are additionally outfitted with a metal helmet and a gas mask, as well as an optional backpack.
The weaponry of the Specters appears to be a form of modular rifle. Its standard configuration is assumed to be the carbine variant wielded by most Rangers. Various longer barrels, sights, extended clips or drums, and bayonets are used to form the other configurations; aside from the carbine, three other configurations have been identified: a bayoneted assault rifle that comes with a slightly longer barrel, extended clip and a short scope, a light machine gun with a bipod and drum clip, and a high-magnification, long-barreled sniper rifle. The first two are used by the sentinels, being fully automatic and capable of laying down immense carnage in a short amount of time. The carbine and sniper rifle are both semi-automatic.