Complex sentence: The teens accept that it might be better for another species to take humanity's place if this is the price of its continued existence; they share a final joint as the Ancient Ones finally stir, destroying the Facility.
Split into simpler sentences: The teens accept that it might be better for another species to take humanity's place if this is the price of its continued existence. They share a final joint as the Ancient Ones finally stir, destroying the Facility.