Constellation Secret: Breaking the Darkness

The starting event of the story ("The protagonist was abandoned as a child, was impoverished and accidentally got involved in a secret room murder case, relied on wisdom to solve the case, met a zodiac inheritor who was about to die, gave the protagonist the identity of a messenger, acquired skills, and found the other 12 constellations, and combined various abilities to defeat the King of Darkness) The contradiction that the protagonist has to face (dark forces infect humans, how do people of the 12 zodiac signs prevent and protect humans from the influence of dark forces)