Spoilers here
This and Gunslinger's post really is a set of spoilers. If you are more into the mystery, here ya go.
Gunslinger is pretty much on except for a couple of things.
For the characters at least, the Others are a vague presence. Except for a few hints (Sanchez for instance) the characters don't really "know" about the Others yet. As writers we have been afforded some hints, but they are still over the horizon.
But the Slayers (or a faction of Slayers) is actually in league with the League. The reason being is that the Slayers are fundamentally a "high tech" outfit, but somewhat isolated. They dominate through technology and not numbers, and therefore are willing to go to great lengths for the acquisition of technology.
Why should the Slayers play for the League and not the Others. Part of this is ideological. The Others, and their forward scouts the Oprezki, rule by destroying present orders and replacing them through rule by terror. The Others would not tolerate an elitest, technologically superior force as the Slayers. The Slayers would be too much of a local threat. But the Slayers, fearing the coming of the Others, would find the divisions of "Fang's World" too unsettling and themselves unable to build the alliances needed to defend it. So they would look to allies also capable of working in secret.
If we go back to Chapter 1, the only chapter where we see the Slayers, there are hints that things with the Slayers are more complex. Fang himself may, or might not, have known about the Slayer program, but its very suspicious that his colleagues are aware. They are the ones that eventually locate the ghoul base and betray the ghouls as well as delay responding to the Kroeger-McKinner meeting that would lead to the eventual capture of Tabis.
Why? Because the Slayers would want to break up the ghouls presence while appearing as allies. This may have to do with control of the reactor. The Slayers could not allow an independent party control of such technology. Furthermore, the Slayers may also be reacting to Kroeger's technology. IN Chap 1, Kroeger (who is assassinated by a Slayer to cover up the failure of the Tabis op) had discovered a treasure trove of weapons to the West. This is an old army base which has resurfaced in Chapter 3 as the Western destination for our train network.
In Chapter 2 hints of the Slayer conspiracy rise again. For one, we get the order from the Slayers to whack Caleb. Caleb, as the only Blade still operating in the Tabis area, had frustrated the Four Horseman's plan and perhaps knew of their conspiracy. Thus Caleb needs to be eliminated. A further hint comes in the destruction of the Blade base. The Blades were destroyed by what a raider described as thunderous roaring, continuous lightning from the sky, and the smell of gas. The Oprezki, using horses, lacks that kind of technology, but the perhaps the Slayers and the League do. What is that technology- poison gas and probably a one or two gunships. That would outside the Others main base, far to the South and below the jungles of Central America.
So who are the League? We have hints that the League is based on a community of Vaults to the East that have been trying to rebuild. But they aren't very nice folks. Hungry for slaves to work their factories, farms and to serve as soldiers they are attempting to manipulate events in Fang's World for their ends. The Raider blocades of the different cities was an attempt by the League to cut off each of the communities for later conquest. The League operates by secrecy and conspiracy in Fang's World. But yes, their motivations are primarily defensive. They know the Others are coming.
Who is worse? That's hard to say. Neither faction is seeking the betterment of mankind. The Oprezki are merely the forward elements of the Others, and they rule by terror much like the Mongols and other groups of horsemen to rise out of Asia. Indeed the name Oprezki may have links to that area. They are moving North and will sweep any opposition they come across. One can imagine the Others as part Mongols, part Khymer Rouge. Not nice folks. The League, which relies on slavery for labor and resorts to force over diplomacy is more an oligarchy of a few folks who really believe that repression and force are the way to go. Think Blood and Iron. They are fairly ruthless and as we may see, rather prejudicial. I imagine the League to be more like post-apocalyptic Nazis.
So there we are, between a rock and a hardplace.
The central question for the characters of this story. Lately we have been talking about the problem of "who are you, really?" for these characters. Each one of the characters that have come over from Chapt 2 are dealing with some variation of that question. New characters are still getting caught up in the story.
But the next question is "what do you do?" Are you going to join one or other faction, will you try to hide, or will you try to stop them through some other way. Who you are should shape what you do. Good stories require both interesting plot but also good characters.
This is a lot of spoilers which I was hoping to reveal slowly, but ok, its important for us to know who is who.