Rohan, the navigator of the spaceship Invincible, which has been sent to explore the planet Regis III. Some time before, another spaceship, the Condor, landed on Regis III. Less than two days after arrival, the Condor sent a garbled message and then ceased transmitting. The Invincible has been sent to learn what happened. Rohan, the protagonist of the novel and the only substantially developed character, is an Everyman who rises to heroic stature. Like his fellow crew members, he is horrified by the discovery of the Condor, whose crew—all dead—apparently went mad. Like his comrades, he comes to fear and loathe the force that opposes them on Regis III: swarms of tiny crystalline forms that swoop and scatter like insects and form enormous pulsing clouds with great electromagnetic power. Rohan’s triumph comes not in the victory-by-force of the conventional hero but in the recognition—even appreciation—of this “black rain” as an independent form of existence, however alien to humanity.
Horpach, the astrogator (commander) of the Invincible. A gray-haired veteran, tall and broad-shouldered, decisive, and seemingly unflappable—a virtual caricature of the steely military leader—Horpach is revealed to be human and vulnerable in a crucial meeting with Rohan.
Lauda, the chief biologist of the Invincible. Like Horpach, Lauda is a veteran, unusually old for spaceflight. It is he who first proposes that their enemy on Regis III is the product of eons of inorganic or “machine” evolution, a hypothesis that is confirmed by subsequent events.