Boundless Necromancer is a Manga/Manhwa/Manhua in english language, Action 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

[By the studio that brought you and !] I never thought I could become a hunter. I never thought I’d get the chance. But that wasn’t the case. 「 The ‘Tower of Trials’ has selected all suitable candidates from Earth. 」 「 Please select your difficulty. 」 「 The rewards you get will be directly proportional to your chosen difficulty. 」 I was given a chance just now. A special one, at that.