The King

Family
The King was born to a human father and an Elarian mother. His mother was one of the Guardians. His father was abusive, which turned into the King hating humanity for all its wrongdoings. His mother was a Guardian but she wasn’t a ruler, only an advisor. The King disapproved of this, thinking things needed to change. So when his mother passed down her notebook to him and he became the new Guardian, he used his power to take control of all of Elaria and separate the connection between the two worlds, finally protecting Elaria from human cruelty.

Royalty
The King often got into arguments with his human partner. Eventually, the King killed off his partner, leaving only himself as the Guardian. This means he would begin to age again. To combat this, the King began killing two birds with one stone. He would search for a new successor, someone with similar morals and beliefs. And if he didn't like the person he began testing, he would just kill them and take their soul to make himself live longer. He has never found someone he thinks can fill the role as king, and he never will. At this point in time, it has been thousands of years since the King killed his partner, still searching for a successor too perfect to exist. To Earth, dragons and elves are just myths. And to Elaria, humans are simply myths as well. The King continues his search for the perfect successor.