Essence [n.] the spiritual energy of one's soul; the divine spark of life.
In that divine moment when the All-Father breathed life into the first Mortal; it is then that He blessed them with Essence. It was then that He gave them power. Essence flows throughout all of creation. It is in the waves of the sea, the wood of the trees, the clouds in the sky, and the wind in the breeze. It is the soul of creation. It can be channeled and manipulated by various creatures; creating both miraculous and disastrous physical effects.
For mortals, these arts were once a sacred and cherished discipline, and way of life. To be used for the betterment of all children of the All-Father. When the first Elementals were born, they were immediately seen as blessings. Mortal beings born with the unique affinity and ability to create and control the very Essence of the Elements: Earth, Fire, Wind, Water, Ice, and Lightning; the All-Father had bestowed upon His children the keys to the elements. Nations prospered, civilization flourished. All was well.
Yet when such knowledge, such power, is given; it then succumbs to its own hubris. War, it can't be escaped. Vast armies appeared, headed by the most powerful of Elementals seeking to spread their influence. Wielding Essence and the elements these armies did battle. Then the time came when all learned of a new breed of Elemental. These controlled a deadly element—Tox.
Able to control and create the very poisons of death; their rise pales when in comparison to the arrival of those wielding the element of Darkness. Storming nearly half the universe in a tyrannical campaign for supremacy, they were finally halted by an army of those whom wielded the element of Light. The very Essence of Life and purity at their disposal; they waged a valiant war with the dark armies. The battle would end in a stalemate.