I'm trying to locate a pre 1980 sci-fi novel. Alien spheres have suppressed all electrical technology, and on a regular basis try to transport earth to their dimension, "Hell Day".
A pair of rings from bottom of a sphere are recovered and can be used as a dimensional transport or as a source of fundamental matter which can be shaped by the power of thought.
Humans have one advantage, they can work this stuff in groups. I think the title had the word "sphere" in it
This is Lords of the Psychon by Daniel F. Galouye.
Please note that it was "Horror day", not "Hell day" but pretty much everything else matches.
The novel is set 15 years after the devastation of earth. A band of holdout soldiers remain steadfast to their military/defensive duty, and are based in a deserted junior college in the shadow of a strange, towering, alien City of Force. 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 the aliens, and all of human civilization has been driven back to a coal and steam-based technology. The Cities of Force are the home of the “Spheres”. They are large floating aliens that generally ignore humans except when they decide to “select” someone. Then they hover and float through the air, crackling with static electricity and hunting the selected person apparently for sport. Spheres can travel right through walls and hillsides in their pursuit of the selected people. When they finally run down the prey, they throw lightning bolts to kill the human. The Spheres also get active around the time of Horror Day, an annual event when a grid of energy forms over the earth and somehow inflicts incredible physical and mental torture on the earthlings, which takes months for the populace to recover from.
