Celestial Law

Innocent life is to be preserved at all costs.
Threats from outside the Mortal Realm hold priority in all duties.
The Celestials must guide and advise the Mortal Realm, but not shape it's destiny.
Magic is as sacred as life, the knowledge surrounding it must be gathered and protected.
Darkness must not be feared, but kept in the right hands.
Time and Fate must not be tampered with by anyone but the Guardians of Time.

The law set by the Celestials upon creation of the universe, they worked to enforce these tennets and bestowed the duty of doing so upon various groups of mortals too. They are not immutable, objective laws of nature, and so they have often been forgotten, disregarded, or outright opposed throughout history. Only people who revere the Celestials adhere to this law these days, although if one's soul goes to The Glow after death, this is what they are judged upon.