From The Big Fat Book of Magicalia: Edition 3- Common Spells and Magical Rules

Magic is a powerful energy, being a fifth state of matter. Raw magical energy is powerful, and even holding it can result in devastating consequences. It is more powerful than plasma and unlike plasma, is in every single object.  Due to the unpredictability of raw magic, those born with magical capabilities are almost always subject to magic binding, to keep their powers in check until they grow to handle their full potential. Almost all bloodlines are bound by this curse- not that it is much of one-, so those who are not born bound are subject to death because their magic consumes their very essence- unless, of course, they are the children of very powerful witches or deities, in which case the mere presence of these witches subdues the dangerous effects while keeping the positive ones. These witches are almost always with guardian angels due to their magic being powerful enough to tip the scales of balance one way or another.

Magic is somewhat bound by the very laws of the universe, as well as some unique ones, so knowing the rules can help avoid consequences. While not the most important, the most well known is the rule of consequence- One cannot use magic without consequence. Most of the time, it is merely fatigue, but in other cases, it can be physical deformity, unfortunate luck, or some other consequence. Those who can use magic without consequence are amongst the most powerful witches in history- Merlin being one of them.

Other rules include the collateral rule. While one can use magic for personal gain, they cannot do so if it would cause harm to others without consequence. For example, one can rig an election to have more votes for themselves without consequence, but will be punished should they choose to instead fill their opponent's vote box with blank sheets of paper. Unfortunately, using magic for malicious intent and having a side effect benefit the caster does not fall under this rule.

The rule of decision is amongst the most powerful, as not even the greatest witches were able to overcome it. When a supernatural begins to develop power, they alone must choose whether to use it on the side of good or the side of evil unless otherwise dictated by prophecy.  One can influence them, but it must remain their choice. Their choice to change sides also falls under this rule. This rule seems to be a rule that magic is bound by, rather than a side effect. It ensures that supernaturals fulfill their calling rather than being forced into evil or good.

There are also magical laws. Most important of all is to never cast a forbidden spell without first examining the following conditions.

Eschacense ( a spell that passes through all known shields and results in unrevivable death)- may only be used if no other option to kill a great evil exists. It may not be used for any other purpose.

Perimulum (a spell that causes massive pain to target)- may only be used if all other ways of extracting information from a great evil have been exploited. It may not be used for any other purpose.

Spiriban (a spell that painfully drains the spititual life force of ghosts and other similar supernaturals)- may not be used for any purpose with the exception of killing the Ghost King.

Nexchancy (a spell used to trade a living soul to revive a dead one)- may not be used for any purpose.