The Power Theory/Law states that no one being can have all the abilities, or even a great percentage of all abilities, available without paying some dire price.
It's really simple. No elemental can channel all 8 elements. No shifter can also master glamour. No mage can also be a significant channeler. No one can be a ruler of multiple realms.
If any being is any of these things, as soon as they use even a fraction of their power they die.
If any being comes close to these limits they will suffer from trauma and insanity.
There are exceptions, but it's rare.
Exceptions include the Chosen Ones or Guardians, people who the dimension itself selects to be the best at one power. To be a Chosen One, the dimension must see you as the best choice for the power. More often than not, Guardians are Chosen when they are born and can access a special Chosen-One only Realm through a self-made portal called the Guardian Realm. Only Guardians and their servants are allowed to be there and it is impossible for anyone else to infiltrate since if someone other than a Guardian tried to walk in; they would die.
Even people as powerful as Noemi and Lotus before her have their limits and suffer greatly for their power.
Going along with the Law of Creativity, one cannot obtain too much power in the dream dimension or they will die and become Unconscious forever.
Things work this way to balance everything out. If there were a large number of greatly powerful people the world would be thrown into chaos. Not to mention all the possibilities that would arise.