Complex sentence: The black smoke, or black powder is a fictional poisonous gas in H. G. Wells' science fiction novel "The War of the Worlds", used by the Martians to eliminate groups of humans remotely, especially artillery crews, before they could fire.
Split into simpler sentences: The black smoke, or black powder is a fictional poisonous gas in H. G. Wells' science fiction novel "The War of the Worlds". It was used by the Martians to eliminate groups of humans remotely, especially artillery crews, before they could fire.