A Lich was an Archmage that voluntarily cast a forbidden spell to transform themselves into an undead in their pursuit of immortality. 

Whereas when a skilled knight became an undead, they became a Death Knight.

If that's the case, then what about that one country's king, who was transformed into the undead through a curse?

"That's the Immortal King?" Eder asked.

"Yeah. The Immortal King, Arumode."

A long time ago, before the rise of the Altein Empire, there were several countries on the continent vying for supremacy.

It was like the Warring States period in China, the Sengoku period in Japan, or the Three Kingdoms period in Korea.  

During this time, there existed a weak and tiny country called Graham, which was ruled by Arumode.

The Kingdom of Graham was invaded countless times by its neighboring countries.

With the Kingdom on the verge of collapse from these constant invasions, Arumode made a radical choice.

He had decided to use Katan's cursed keepsake; Katan had killed the most people in history and was subsequently known as the most notorious mage. 

As a result, the capital was engulfed in death magic.

Arumode, the royal family, the nobles, and even the civilians were unable to avoid death.

The soldiers...