On the surface he is a charismatic, successful Emperor, however his true personality was revealed to be a heartless, sadistic, power-crazed man that had no qualms commanding Gang-Hui to massacre a whole village of children for supposedly 'opposing him'.
He was the ruler of Dae-Hyun 150 years ago after his father, the previous emperor fell ill.
He possesses Divine Power despite being a male, and is extremely powerful. He was able to retain his memories after being sealed by Ga-Bi and was reincarnated seemingly from his own will.
He is obsessed with Ga-Bi during his youth and time as Emperor that later is revealed to be because of his obsession with her Divine Power. This then extends to Hong-Ryung as he currently possesses his mother's powers.
In his reincarnated form as Dong-Hyun he initially fooled Hong-Ryung by rescuing him and promising to become his ally, to find where Ga-Bi was sealed. Later on he reveals himself and is attempting to obtain the powers Hong-Ryung possesses.