Complex sentence: Wherever the aliens have established themselves, they have raised up great walled citadels-palaces comprising huge buildings shaped like cylinders, pyramids, cubes, rhombohedrons, semi-transparent prisms, and balls-while electric equipment all over the earth has been shut down by force.
Split into simpler sentences: Wherever the aliens have established themselves, they have raised up great walled cities comprising huge buildings shaped like cylinders, pyramids, cubes, rhombohedrons, semi-transparent prisms, and balls. Electric equipment all over the earth has been shut down by force.