The Niners

The Niners at this point in time resemble the fiends a little too much in my opinion, and as opposed to being just addicted to drugs( or chem's as they are called in Fallout) they instead should worship them. Maybe they see these drugs as not just narcotics or a way to get a decent high but a way to connect with their gods( in their minds anyway). For instance, maybe they treat different kinds of Chem's as representing different gods and that by using them they "inject" a bit of their god into themselves. An example would be warriors going into battle interpreting Psycho as a means of channeling the god of war or using Jet/Hydro to temporarily channel the god of time.

The leaders of their society would be the ones able to take the greatest amount of these drugs at once and not die, as by injecting many of these drugs and being under their influence they could be seen as having a higher state of mind(akin to shamanism perhaps, as that religion is characterized by entering an altered or spiritual state of mind).

Unfortunately due to this their life spans are shortened greatly, as even their elders are barely 30 and due to the constant use of chem's look much older and worn than their age would suggest. To the Niners they would interpret this as the gods taking a bit of their mortal being as tribute whenever their power is accessed, and eventually their entire being or soul is taken.

As one may think they gladly participate in the chem trade and make dealing with whomever they can for said chems, often giving meat or other raw materials as payment.

They are in fierce competition to the Shoshone, the Iron liners, and the Cheyenne Braves though they are on better terms with the Khans due to them being their new primary chem suppliers.