The Gray Mark is a Manga/Manhwa/Manhua in english language, manhwa series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

The ruthless criminal “Great,” exiled to space for his countless crimes, is banished to the past alongside the King of the Universe, “Rohollah,” after their encounter in space. Great attempts to right the numerous wrongs he committed in the past to try and rewrite a better future…