Gate of Nightmares is a Manga/Manhwa/Manhua in english language, MONSTERS 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

This story tells about a fantasy world where dreams and dreams of people come together, pouring out into reality. And where there are good dreams, there are nightmares with fears that turn into real monsters.