Bates, Weisman, Kayanan, and Tanghal conclude the origin of the Silver Shield, and fill in the blanks in the backstories of other characters, in Captain Atom 36 (Dec 89).
Like the last issue, this one cuts back and forth between events in the present, as the Silver Shield telepathically communicates with Captain Atom and Major Force, and the past, as we see Dr Megala and his team experiment on what they believe to be a spaceship. The Silver Shield seems to have been "born" within the quantum field, and found a hole to the reality we know. It took on the ship form to travel through space. It was intrigued by all that it saw, but wound up flying, or swimming, as the Shield calls it, too close to Earth. Gravity got hold of it, pulling down to crash onto the planet.
When Dr Megala, Sarrok, and Babylon's parents tried to use a laser on the Shield, it thought they were trying to communicate, and appreciated the energy. It tried to communicate as well, but that only took place when Babylon's father pierced the Shield with the X-ionized knife. The Shield at that point made mental contact with Sarrok, which overwhelmed the man, sending him into the comatose state he remained in for years.
Captain Atom and Major Force get this story in bits and pieces as the Silver Shield flies around, fascinated by everything it sees. It winds up heading to Las Vegas, creating quite a stir, until Captain Atom persuades it to head back into the desert. The Vegas scenes are also pretty funny.
The energy blast emitted when the Silver Shield was cut killed both of Babylon's parents. Their bodies somewhat shielded Megala, though the energy would have a lasting effect, slowly destroying his body, leaving him looking the way he does now.
Neither Captain Atom nor Major Force really want the Silver Shield to wind up in the hands of Megala and Eiling, and telepathically Atom comes up with a plan. The Silver Shield forms itself a mouth, and announces that it is leaving the Earth. Captain Atom pleads with it to stay, and Eiling and Megala watch all of this through the cameras implanted in Major Force. Atom and Force do their best to stop the Shield, but it flies away and leaves Earth. Or so it seems.
In fact, Captain Atom is now concealing the Silver Shield on Earth, keeping him, for the moment, in Yarrow's old offices. The story closes on other Silver Shield-type creatures, who registered the cry of their brother, and start heading to Earth to find him. I am not sure they ever wind up arriving, though.