Black Serpent 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

In the final battle against the Demon Cult, the Black Serpent leader Jeonghwa was betrayed by the Murim Alliance, losing all her comrades. Barely surviving, she swears to eliminate both the Demon Cult and the Murim Alliance who drove her comrades to their deaths. “Heavens! If justice truly exists… grant me the opportunity to avenge my fallen comrades!”