The Quintessence is a level of power that has been granted sentience, it is granted unto a person who has total understanding and manipulation over a field but still not many people have been bestowed.
This is because the quintessence itself pose great danger to those who try to obtain it or assimilate it to suit their needs, resulting in many deaths, this has caused many experts who wish to attain this power to change their mind for fear of death and for those who have attained this level, they are seen as gods in the supernatural community and the title Sovereign is given to them
As of now, only two people have been mentioned to have reached this level.
Jeremy Krijinaviskar the last of the Viskar brothers but he has not assimilated it completely and made it his thereby it is not suitable for him to use.
Kevin as Finn Montgomery incarnate, the honorary member of the Viskar brothers. Though he wields an unknown quintessence which according to him he is unable to use now for unknown reasons.