Complex sentence: A mad religious leader known as Henry, seeks to awaken the ancient and malevolent god Hastur, by offering a sorceress, Restiana as a sacrifice which will bring the inevitable down fall of mankind.
Split into simpler sentences: A mad religious leader known as Henry, seeks to awaken the ancient and malevolent god Hastur. A sorceress named Restiana, offers herself to Henry as a sacrifice, for a cause which will bring the inevitable down fall of mankind.