The three realms

Managed it.
This one doesn't exactly have much of what one would call 'conflict'. I think there is probably enough here that there would be a significant number of stories to tell in this world without one, plus I may come back here at some point.

As every child knows, the world is divided into three realms.
The topmost, is the Realm of Fire, which lies closest to the uncompromising light of creation. Strange creatures live there, short lived things that seem to be made of fire.
The bottommost, meanwhile, is the Realm of Ice, and it is as cold as the topmost is hot, far from creation’s light. Nothing lives there but the spirits of the dead, who roam that endless realm wrapped in an eternal melancholy. It is a slow place, too, each day lasting a full month in mortal reckoning.
And then, there is the middle realm - the familiar world of humanity, and of matter. It is special because it is connected to the two other realms, by means of two great portals in the sky. There is the life-giving Sun, which connects the mortal world to the realm of fire. And there is the pale moon, which connects the mortal world to the realm of ice, waxing and waning with the days and nights of that realm.
Mortal magic depends upon one of the three reams. Those who draw upon the Realm of Fire, are empowered by the presence of the sun, and when it is not in the sky, they cannot do magic at all. Similarly, those who draw upon the Realm of Ice must rely upon the pale moon, and when it is not present, they too are powerless.
And then there are those who draw upon the native magics of the mortal realm, which obviously is not blocked, as long as one remains in the mortal realm. Not only this, it is far closer than the other two realms, so there is no need to go through the difficulty of drawing magic from another realm - those who draw upon the magic of the mortal realm have no need of the unwieldy and inflexible rituals upon which other magi must rely.
But that is not to say that the magic of the mortal ream is always more useful. For the creatures of the mortal world draw naturally upon its power. It is what allows them to accomplish great feats, and to make heroic efforts. Devoid of it entirely, most creatures of the mortal realm cannot even move.
And the mortal realm is far more populated than either of the other two - meaning that there is far more call upon its power than upon the magic of the other realms. The magic of the mortal realms waxes and wanes in strength - and is often weakest when it is most needed.
One might expect the mages of these three schools to be opposing factions, each convinced of their own superiority. In fact, little could be father from the truth - the three schools relate to each other much as different scientific disciplines do, defined more by friendly rivalry than genuine hatred.
In fact, the mortal realm is in most ways like any other human world, divided amongst squabbling mortal nations. The main influence  of magic has been in allowing technological innovations which would otherwise be impossible for a world with its current level of technological development. The most major part of this is the potential for widespread magical destruction which could take place were a powerful enough group of magicians to open  a new portal between the realms. The politics of mutually assured destruction have thus come early to the more powerful nations.
Further, whilst magic drawing upon other realms is difficult to start, it is almost self-sustaining once the spell is cast. Thus, magic is used frequently to replace technologies not yet discovered - the power of the Realm of Fire, for example, is used in transportation, for everything from hot air balloons, to extremely lightweight steam-engines. The power of the Realm of Ice, on the other hand, is often used for preservation of perishable goods - allowing them to be easily transported across the whole continent - though the ability to call up and talk to the spirits of the dead (albiet with great difficulty) cannot be overestimated in usefulness.
The magic of the mortal realms requires the mage to be more immediately present than does the magic of the other two realms, but is useful nonetheless to those who can afford one. Even the most novice mage of that school is able to give to unmoving things that same motive power which humans enjoy, is able to run like the wind  and to create buildings almost out of nothing. Magic, therefore, is ubiquitous amongst those who can afford an education - it is never not in demand.