While the Earth was still new; before the first human touched the soil of the planet, there existed a great utopia, and two deities charged with keeping the balance between the dark and light. These deities were known as Grimm and Gaia. For all of time, Grimm would take the life from all flora and fauna in existence and return the souls to Gaia, who would give them new life in another form. This was the way of the old world and for many centuries this kept the universe balanced.
As time wore on however, Grimm began to let his darkened emotions take control; envious of Gaia's ability to give life, he sought revenge upon her. Grimm found way to cast out his corrupted emotions and placed a curse upon the Earth in the form of humanity. Gaia found it difficult to replenish the life as these mortals, being born of sin, destroyed far quicker than she could create.
Eventually, the sin of humans gave rise to seven demon princes who sought power from those who committed one of the seven sins. In an effort to rebalance the universe, Gaia too cast out her emotions, giving humans the ability to judge for themselves what was right and wrong. Soon, humanities kindness gave rise to seven archangels who could oppose the seven demon princes.
As a result, a great war ensued over the balance of the universe and for many years Gaia cried, eventually flooding the Earth in her sorrow. The death of so many souls all at once gave birth to four new deities; Aamon, Sandalphon, Abezethibou, and Zadkiel. Aamon and Sandalphon, equal in wisdom and power, agreed to maintain the balance of the universe; while Abezethibou and Zadkiel took the responsibility to hold the gates between the Realms.
Grimm and Gaia agreed to stay within the Living Realm to watch over humanity. Gaia continued to give life to returning souls and Grim would cast judgment upon the souls departing. Since Grimm no longer wished to be responsible for only the death of the living, all flora and fauna were given a lifespan and thus, the Living Realm would forever be known as the Mortal Realm.