Taking a nap after reading this thread has caused me to think of an interesting (to me anyway) take on Magic that I may use in a setting/campaign I run in the future.
Magic is ultimately freedom from and rejection of the physical universe and its laws, as by its nature magic ignores and breaks them. But the universe reacts against magic and bends causality to try to diminish the ability of magic to reject the physical laws.
This will manifest mechanically by the cost of magic not being mana, spell slots, or anything else like that. All use of magic results in penalties to future rolls, and other random or DM decided occurrences, that impact the magic user, the duration and magnitude of which depend on the power of the magic used. The power of magic a wizard can use will not be limited by skill or experience, instead the magnitude and duration of penalties can be reduced as more experienced wizards understand how better do magic in a way that minimizes the universe's backlash.
The backlash also manifests itself in consequences for those closely working with, associated with, supportive of, or maybe even just physically near the wizard, especially for more powerful uses of magic.
The magic system would also want to very strongly encourage free creativity from magic using players in thinking up the magical effects they would like to cause on the fly, as opposed to a list of very specifically defined spells.
As a result wizards tend to be very individualistic, chafe at restrictions, and prone to selfish motivations. Many may philosophically view the universe as a trap to be escaped from or defeated in some way, while societies and others tend to view them, and magic in general, as a source of danger to others. Both due to the power they can wield, and also the impact of the backlash their magic use causes on those around them. The universe bending causality to react against the magic also provides additional reinforcement for societal norms that reject magic.
There would also be anti-wizards. They would be wizards who use magic, but use it in a careful way that is done to counteract and mitigate previous uses of magic. Magic used carefully in this way would not produce little to no backlash from the universe. The way anti-wizards would manifest in society would likely be strongly tied to religion and authority and may take on the social form of divine magic, or magic done in accordance with the will of the gods/religious powers.
Just the initial spark of an idea though. Needs some more thought and iteration.
Also, I am sure someone is about to provide a link to some system or setting that already basically has magic work this way showing I am not original in any way.
