Complex sentence: One of the Ontongard, named Prime, was a mutation who rebelled against the hive, sabotaging the invasion mission ultimately leaving most of the personnel stranded in suspended hibernation in the starship on the surface of Mars.
Split into simpler sentences: One of the Ontongard, Prime, was a mutation who was somehow independent of the hive mind. He rebelled against the Ontongard, sabotaging the invasion mission and ultimately leaving most of the personnel stranded in suspended hibernation in the starship on the surface of Mars.