Mage: the Ascension is very complex game that can do all sorts of stories depending on the GM’s preferences. In fact, I would highly recommend that a GM who plans to run Mage: the Ascension should really take the time to decide what the campaign should be about in order to lend focus to the game.
One of the easier ways to do it is to look at two things: Scale and Conflict
This is where we discuss the scope of the game. Mage: the Ascension can go all out and tackle things like the far realms, alternate dimensions, fighting in the spirit realm and other locations and times.
This suits games of high adventure very well, but there’s also an opportunity to run games that run the opposite end of the spectrum. These are the low-key street level tales of mages who struggle with every day life and work to improve their immediate community rather than trying to change the world.
By selecting the scale of the campaign, the GM can then work on creating the kind of opposition, situations and conflicts that work within that range. Mood and tone of the campaign are likewise influenced.
It is impossible to have a game about having an Ego strong enough to change reality, and not run into conflict. Mage is all about having people with powerful wills with agendas that don’t agree with each other. As such the conflicts that best suit a mage game are those that have valid motivations.
Nobody is truly evil in a mage game. Everyone just thinks that they’re the good guy, even the ones that sell their souls to demons to get what they need believe that they’re protagonists… in their own twisted way.
Mages are very good investigators, and can easily be exposed to all the sides of a conflict. My preferred methodology is to get the players to realize why the opposition believes what they do, and see how the players plan to resolve the conflict (through peaceful or violent means)
Specificity in a mage game’s Scope and Conflicts is a good thing. For the GM, it allows them to bring the game into better focus without being all over the place. Players also will appreciate the consistency of the campaign, as opposed to punching Cthulhu in the face one moment and then worrying about a marriage that is falling apart in another.