It's a mix. The show is based on historical events which are facts. For example, the Viking invasions and the existence of various kingdoms in England during that era are real. However, some of the specific characters' storylines and relationships are fictional. They are created to make the story more engaging and dramatic.
A novel similar to The Kingdom of Death could be recommended as The Ultimate Mad Soldier of the City. The protagonist of this novel was also known as the Grim Reaper. He had great power overseas and became the king of a private country. I hope you will like this novel.
Kingdom Death Monster is a dark and challenging tabletop game with a complex story. It involves survivors in a harsh world fighting against terrifying monsters.
The Qing Kingdom in the Qing years was the Southern Chen Kingdom during the Northern and Southern Dynasties. Although the Qing Kingdom was fictional, its background in the drama corresponded to the Southern Chen Kingdom. The Southern Chen Dynasty was a short-lived dynasty during the Northern and Southern Dynasties. The Qing Kingdom was located in Jiangsu, Zhejiang, and Shanghai. Sigu Jian was the protector of the Qing Kingdom. The Qing Kingdom and the Beiqi Kingdom were opposing each other, and the Southern Chen Kingdom was the only Southern Kingdom that had the ability to oppose the Northern Qi Kingdom.
The Qing Kingdom in the Qing years was the Southern Chen Kingdom during the Northern and Southern Dynasties. Although the Qing Kingdom was fictional, its background in the drama corresponded to the Southern Chen Kingdom. The Southern Chen Dynasty was a short-lived dynasty during the Northern and Southern Dynasties. The Qing Kingdom was located in Jiangsu, Zhejiang, and Shanghai. Sigu Jian was the protector of the Qing Kingdom. The Qing Kingdom and the Beiqi Kingdom were opposing each other, and the Southern Chen Kingdom was the only Southern Kingdom that had the ability to oppose the Northern Qi Kingdom.
The Qing Kingdom in the Qing years was the Southern Chen Kingdom during the Northern and Southern Dynasties. Although the Qing Kingdom was fictional, its background in the drama corresponded to the Southern Chen Kingdom. The Southern Chen Dynasty was a short-lived dynasty during the Northern and Southern Dynasties. The Qing Kingdom was located in Jiangsu, Zhejiang, and Shanghai. Sigu Jian was the protector of the Qing Kingdom. The Qing Kingdom and the Beiqi Kingdom were opposing each other, and the Southern Chen Kingdom was the only Southern Kingdom that had the ability to oppose the Northern Qi Kingdom.