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

Coming out of the depths of our minds after a slow agony, nightmares have come to life. Driven by the sole desire to destroy their hosts, these monsters with their multiple forms have become a plague to be eradicated. Faced with this threat, the Holy See has founded the Epeira caste, which it erects as its armed wing, now the only ray of hope in a world of darkness. Arane took the oath to this order and became one of its most renowned members. The famous dream hunter known to all as the « Boogeyman ».