Hyunckel held a hatred towards his teacher Avan, as he believed that Avan was the one that killed his adoptive father, however, he has a strong sense of honor, as he refused to harm Marm. He also has a sour relationship with Flazzard and Zaboera.
Hyunckel is an orphan that was adopted by the undead swordsman Baltos, who was the gatekeeper of Hadlar's castle. Eventually, Avan and the heroes invaded the castle and defeated Baltos, but Avan spared him. After Hadlar was killed by Avan, Hadlar was revived by Vearn, who angrily killed Baltos. Hyunckel mistook Avan as the one that killed Baltos, so he planned to kill Avan, which ended in failure. Hyunckel was adopted by Myst-Vearn, and thus, Hyunckel eventually became one of the leaders in the demon army.
After the defeat of Crocodine, Vearn sent Hyunckel to defeat Dai. Hyunckel then destroyed the kingdom of Papunkia and encountered Dai and his friends. At first they mistaken Hyunckel as their ally, but Hyunckel summoned some skeletons to attack them and told them that he is the leader of the undead knight division. After the skeletons were dispatched by Dai, Hyunckel fought them and easily defeated them, explaining his backstory to them. When Hyunckel was about to kill Dai, Crocodine appeared and took the attack instead, thus giving a chance for Dai and Pop to retreat while Marm was imprisoned. As for Crocodine, he was greatly wounded and fainted.
After some training, Dai and Pop returned to fight Hyunckel. With Marm's help, who escaped from the prison, they were able to summon lightning, which, although wounded Hyunckel, still wasn't enough to defeat him. Hyunckel processed to punch Pop away and wounded Dai, but then Marm appeared to tell Hyunckel the truth about his adoptive father's death, much to Hyunckel's shock. He refused to believe it, but at the same time, Dai suddenly walked towards Hyunckel and viciously attacked Hyunckel, destroying his armor. Marm begged Dai to stop, and succeeded just before Dai was about to kill Hyunckel. Suddenly, Flazzard appeared and turned the arena into a living volcano as he was unhappy with Hyunckel, who is a human on the same rank as him. As lava started to emerge, Hyunckel threw Dai and his friends away from the arena before sinking into the lava, seemingly killing him.
However, it was revealed that Crocodine had a Garuda to save Hyunckel from his fate. After this, Hyunckel joins Dai's side in fighting against Vearn, ending his villainous role.