I was just thinking about how people ussualy asume there are 2 factions at play. The fun Gang and the Evil Fountaineers.
We think the Knight is working with Carol, we see the Knight go into the Bunker, we think that Gaster is in the Bunker.
Yes, there is the triple truces theory, but that is about spliting the Knight and Carol, which I think work together.
From the ch3 Knight battle Gaster dialogue we know that Gaster is actually rooting for us against the Knight, placing them in oposition. He also talks about "his deltarune", which is his goal.
So we have 3 teams.
The Fung Gang, the 3 heroes, seeking to stop the roaring and subwert the prophesy. Lead by Susie
The Fountaineers (not evil fountaneers), seeking to bring back Dess, possibly by bringing about the Roaring, but possibly by compleating the Prophesy, where the roaring is defeated (at some unknown cost). Lead by Carrol
And the Deltaruners, who seek their deltarune, which can either be some in game "thing", or something more abstract, like the most hype aura moment story. Lead by Gaster.
Some characters have their aliegences split, which I drew kind of halphazardly.
Kris obviously works with the knight but likes the Fun Gang.
Soul likes the fun gang and wants a good story/likes gaster/vessel.
Ralsei is also split because I like the theory that he was created by Gaster, but if not he would be commited to the Fun Gang.
And Friend, who is a Device, so was made by Gaster, but seems to be doing nebulous evil stuff? Which is kind of pro Roaring, which might be pro Dess. Realisticaly, he is either playing the "bad cop" the the "good cop" of Gaster, helping the bad guys to get a more hype story. Or he is in his own 4th faction, that wants to bring about the Roaring and not have it be stoped, which would destroy the world and is not what any of the 3 other factions want.