Magic was once everywhere and could be drawn for almost any reason. Now it is tied up in things. Because of The First Contract most of the magic is tied up in contracts. It is also in the blood of the nobles though. It is even in places. There is enough ambient magic in the very land itself for nobles to slowly regain their magic that they use. This is a slow process though.
There is a story of a greedy little prince. He wanted to harness all the magical energy left in the world. e wanted this because he wanted to wield powers never before seen by anyone. He wanted to create a tornado so large it threw mountains into the air. He wanted to pull the heat from the sun to burn his enemies. So he learned to control magic. He learned all there was to know. However he didn’t learn how to measure it. So he pulled it all into him, but he couldn’t create a tornado, because he had pulled into himself the very power of the wind. He went to burn his enemies, but the sun no longer gave off heat since he had pulld into himself the power of the very sun itself.
You see what the boy had forgotten was that magic was at the very core of all things. And that by taking all of the magic for himself he had destroyed the very things he wanted to control.
Magic is in all things. As something gets removed from it’s original state it loses it’s magic. So ore within the earth is actually more magical then a sword. Mages (or nobility with magic) must invest more magic to aid any changes with their own magic. Magical creatures are the easiest to affect (nobles, dragons, etc.) since they have their own pools of magic, however their magic also resists the change and they have a higher reistance.
So I’ll use the witch’s spell of Hallucination. You are actually tranforming the thoughts in their mind. Since a human has magic (but is unable to use said magic) you can affect them. Since a noble is a magical creature (kinda) you can effect them, but they have some resistance.
All magic is tranformation and the distance you can change it is based on the amount of magic said object has and the amount of magic you invest into the spell. So while it is possible to turn stone into a fireball, it would take far more magic then the stone has and the noble would have to invest incredible amounts of their own magic, which would probably take a very long time. To weaken the stone though so charging soldiers can smash through it would be much simpler.
Expanded Knowledge: In the beginning little was known of magic. Even the most powerful magical minds had very little grasp on what magic truly was. Now things has begun to unravel and we finally have a full picture of what magic is. There are two kinds of magic – Mysticism and Enlightenment. There is a third kind of magic, which has recently been discovered, which is formed when the two are merged. The third kind is a rigid unmalleable form though and to date no use has been found for it.