Okay that title probably made very little sense, so let me explain: I'm writing a story with three main characters that get sucked into this sort of sci-fi/fantasy world which is kinda like the centre of the multiverse but not really. anyways, not important. what is important is that the three characters, a girl from modern day earth, a mercenary/bounty hunter/professional badass from a sci-fi universe, and an elven prince from a fantasy world, all meet and become somewhat friendly to begin with. unfortunately, they get separated and drawn into this worlds power struggle separately, each one into one of the three main factions, thereby becoming enemies. long story short, I need three compelling motivations that are of equally morality, so as not to force readers to think 'yeah, this is the good guy, the other two are working for the bad guys.' the motives of the three factions are still up in the air, but I'm thinking they'll probably be fighting over some ultimate power source and what to do with it. i have already decided that the girl from earth is going to study magic with and subsequently fall in love with the people and specifically the ruler of her given faction, and thus will protect them at any cost, even to the detriment of everyone else. so really i just need two more motivations. any ideas you might have would be appreciated.
Safety, duty, freedom, revenge, nationalism, etc are all good motivators for large-scale conflict. Say character A wants to keep her people safe. Maybe character B disagrees, believing that personal freedom is more important than safety. Character C thinks a balance should be struck, and that duty and responsibility should fall in the hands of citizens, not the government. Obviously you can add a lot more nuance.
Or you could make them all wrong. They could all be fighting for power/territory. That's kind of how it is in real life. The lines are blurred between conquest, defense, and subjugation. If you give them all the same motivation, then that might make it easier to be sure that they're all equal and that none of them are less correct than the other.
It's a Fire Emblem Fates route of "Do I side with these people, these other people, or fight for myself?" kind of thing. If they all are fighting within a three-way war, you could add some more intrigue by having alliances made between the factions. You could even have one faction make secret treaties with the other factions in a power move to conquer everything! Have them all try to make power moves! This is war! There is no morality! Fighting for peace is an oxymoron! Unless there is someone that can be truly called "evil," then there is no good side. It's like comparing the Vietnam War to World War II. At least Hitler was a force that most everyone conceded was evil and needed to be stopped, but everything was far more vague in Vietnam.
