In criminology terms, the Disciples most common factor is the act called 'thrill killing', meaning that they are bloodthirsty and sadistic by nature. The Disciples are more akin to regular wasteland raiders than the Operators and the Pack. Their base in Fizztop Mountain is filled with dismembered corpses and gore.
Since Nisha became their leader, and naming them the Disciples, they follow the natural way of the world: Kill or be killed, survival of the fittest.
The only rule they follow is "Don't get caught.", meaning the Disciples are pretty much free to do as they please, including killing members of the other raider gangs, as long as they don't get caught. Leaving behind evidence that trails back to the Disciples may lead to disciplinairy measures taken from within, which usually means the offending Disciple is killed and disposed of.
The Gauntlet is built by the Disciples, as a way of keeping them calm while waiting for Colter to follow up with the plans of taking over Nuka-World.
Most of their members are women. They are not female exclusive however, since it is possible to find male Disciples in owned raider outposts, and a few can be seen in their base with Savoy being a notable male Disciple.
All Disciples wear face-covering masks. The reason for this is unknown.
The Disciples are one of the gangs the Sole Survivor can choose to help during the Nuka-World add-on. They can do odd jobs ranging from murder to defending their own, and help give them new territories around the park as well as giving them settlements in the Commonwealth. Depending on the ending for the raiders, they can either remain allies or end up being the final bosses with the Operators and the Pack helping you eradicate them.
Alternately, they and the two other raider groups can be destroyed in Open Season.
Disciples usually carry a .44 pistol with a bayonet, or a shortened, automatic version of the handmade rifle in their gang colors, with modified versions of this gun commonly equipped with drum magazines.
Disciples faction armor offers a fair amount of well-balanced protection akin to combat armor, but is almost twice as heavy. Their custom metal armor weighs up to 109 pounds for a full set while providing even higher resistances than a suit of heavy combat armor. Since every single Disciple is equipped with at least a few parts of their armor, it often means that even the most basic Disciple boasts better resistances than raiders or Gunners of much higher levels. This, coupled with their powerful weaponry, makes them a lot more dangerous than their Commonwealth counterparts regardless of player level.