Hadlar is one of the Demon Lord's commander's. He fought Avan years ago and lost, although Avan thought he was the Demon Lord at the time. His body is able to regenerate due to one of the other commander's power so he eventually revived and came back to fight again. 

He fights Dai and although he loses his body has the ability to regenerate still so he waits to heal himself up before trying again. Her is very humiliated by the fact that he was beaten by a child though and is determined to avenge his loss. 

I picture his to have a deeper and menacing sounding voice. He was originally thought to be the Demon King so I would like him to sound similar to what you would expect a Demon to sound like, maybe just not quite as dark.