The Chairman of Pharmaceutical Company is a Poison King

A brief description of the manhwa The Chairman of Pharmaceutical Company is a Poison King:
300 years later… On an Earth shrouded in mana. I was a ‘Mana Rejector’—someone for whom that very mana was a deadly poison. Then one day, as I was waiting for death, unable to even Awaken…I connected with an identical soul from another dimension. The soul of the Absolute Ruler of the Murim… The Absolute Poison Demon, Dang Gunak