I Really Didn't Pick up the Mage Tower

A long time ago, there was a terrifying Shadow Demon King in the Continent of the Gods. In the records of the Saint-Imilan Empire, he is: The assassin of the bishop; The demon king who eats raw hair and drinks blood; The messenger of hell who summons evil spirits; A ghost that won't die even if its head is cut off... Among the people, there are also legends about him: Eat chicken without plucking the feathers; Eat fish without scratching the scales; Eat chestnuts without shelling them; Eat people without spitting out bones... Children stop crying when they hear it, and adults fight when they hear it. Because of him, shadow magic has become taboo, and any user will be unconditionally hunted down by all the forces on the continent of the gods until their heads fall to the ground. The boy who traveled through time unexpectedly obtained his inheritance. In the past, you could make shadow magic a taboo, so now, why can't I make it a superior way that everyone respects!