Art Magic and BWG

I got my hands on the Magic Burner at last (I know codex is around the corner). So Art magic is broken down into a variety of actions, and then various schools have access to a portion of these actions via how ever they set up their Schools.

I am trying to teach my self the Art Magic system and come up with an idea for some schools, but i am not quite sure what the various Dice of school really mean? What does a D3 offer more then a D1? Would a D1 only have access to a few actions while a D3 maybe all of the action types? How do you determine what a school can or cant do?

I think i understand the

I wanted to make a WarMage school, but i dont know what limits to set on such a school. Obviously i wouldnt have him try to Control Weather or any really BIG magic. I would keep it focused on hey would this be useful to a WarMage?

Boost Moral of Allies (Advantage) or Negatively Affect an Enemies (Hindrance),
Sorcerous Weapon and Destroy with Sorcerous fire are self explanatory
Maybe Arcane Knowledge would be good for like Tactics or Something?
Evoke for bashing down doors or something…
Transformation and Illusion i can see uses but idk if they would prove too useful for such a school

Maybe I am trying to do too much with one school, maybe i would have to break it down into smaller schools. Maybe break it down into Disciplines like: Mind and Body or something.

The number of dice is just that: how many advantage dice you get for spells of your school. It’s how powerful that school is. So a 1D School of War would give an extra die for war spells, and a 3D School of War would give 3 extra dice. It’s as simple as that. You can think of it as how potent the teachings of the school are, or something to that effect, but that’s window dressing. The mechanics are just advantage dice.

How limited to make schools is a matter of taste. The broader the school the more powerful the school is, of course. The schools are more intended to fit certain methods and use that certain sets of actions. So it’s not that you get or don’t get one of the nine effects, it’s about how they work. Advantage to Steel makes sense on a battlefield; advantage to Resources doesn’t. Illusions of smoke or fire that contribute to fog of war might be fitting, but detailed illusions for entertainment wouldn’t. Transforming into a Troll seems useful for a big fight, but not turning into a sparrow. And so on.

A simple rule to use for this is that war magic might anything that harms people. You can hinder enemies, call fire down upon them, or even turn them into newts. You can’t bolster yourself or turn yourself into a Troll to squash your foes or even conjure weapons; that’s not the kind of brute-force magic that war mages use.

Which one’s correct? Your choice.

Of course, you can also make the argument that an advantage for Resources is great as a logistical edge in supplying armies. Maybe supplying traits like Tough is right on point. Convincing illusory squads make for excellent battlefield misdirection, and turning into a small bird for reconnaissance is perfect for a wizardly tactician. But then your school of war looks like a school of battlefield tricks, and I wouldn’t give access to the direct, brute force tools of actually slaughtering people.

It’s all up to your tastes and those of the other players at the table.

I’d go the more subtle route and have different schools, for example a School of Illusion, School of Fire Magic, School of Oriental Magic, etc., and then show your wizard applies his sorcerous knowledge to the field of war.