Frankenstein (Kor. 프랑켄슈타인) is Raizel's devoted servant who has loyally served him for over 820 years. He is also the founder and current principal of Yeran High School.
(*1) The book mentions he had been with Raizel for over 1,000 years. Thereafter, he searched for Raizel for 820 years. Plus, predecessors mentioned Frankenstein lived longer than normal humans; from which we can infer he probably lived well more 100 years.
Frankenstein is a character that sometimes plays a more protagonist role than the main character.
Superficially the chairman and principal of a private Yeran High School, he is a handsome, tall, blond-haired man who runs a low-tuition school with love for his students. However, he is in fact a faithful subordinate and butler to Etrama Raizel with special mental connections. A loyal servant, he wandered 820 years to find Raizel who had disappeared.
Frankenstein is an impressive scientist, who had done an immense amount of research on human modification, before Raizel's "disappearance". All the research he had conducted was recorded down in his journals. The Union stole some of Frankenstein's records and using this, they created the Dark Spear. Seeing the great danger for humans that comes with the Dark Spear, Frankenstein took it from the Union. One of Frankenstein's journals was found by the Union 540 years ago and another was found by Dr. Crombel 130 years ago.
Frankenstein's true identity was revealed by Gejutel. He is apparently a human with powers that matched the previous clan leaders and is stronger than the current ones. He obtained his powers through continuous experimentation on himself and nobles. Many stories have originated with him in the human world, including tales of humans giving their souls to the devil in exchange for eternal life, mad scientists pursuing knowledge to attain eternity, and so forth.