The Dark Magician Transmigrates After 66666 Years is a Manga/Manhwa/Manhua in (English/Raw) language, Adventure 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

Diablo Volfir, a mighty magician, was sealed for aeons due to the schemes of the 12 Gods, but 66666 years have passed since then, and he descends to earth once again!