Prince Tarkan was King Veha's adoptive son, the previous wielder of Kheiko, and the previous crown prince of Aldra. Despite being important to the story isn't much known about him. King Veha found him on one of his journeys through Aldra, while on the border he found the abandoned infant. While believing it to be a trap he still decided to adopt the child to be his heir as he had yet to find himself a queen.
While still he still was very young, the warlock Sherpa confronted King Veha about abducting his child and the two kings entered a truce, Sherpa would take King Veha's heart and wouldn't touch Aldra, while King Veha would bring up the boy and raise him to be king. Not soon after Amyrst is implied but not directly stated to be his birthmother posing as an innocent woman arrived at the castle, to become Prince Tarkan's nurse and take care of him while King Veha was out seeing how the population was faring although gradually spending less and less time in Erdra.
As Tarkan grew older it's implied he and Amyrst started an intimate relationship giving her anything she wanted and letting the population suffer as a result. It's said that Veha eventually exposed the two being together, and banished them. Amyrst turned into an owl, Prince Tarkan into a mere thought/idea, and Kheiko sealed until a chosen one would wield it against him.