Complex sentence: The conflict in "7th Legion" takes place in the future, distressed from rampant overpopulation and reckless consumption and pollution of Earth's precious natural resources, the many industrial phases of Humanity ravaging the planet's ecosystem to a critical point.
Split into simpler sentences: The conflict in "7th Legion" takes place in the future. Rampant overpopulation and overuse of Earth's natural resources have regressed the planet's ecosystem to a critical point.