19 - Wandl the Invader by Ray Cummings

In a universe where nine planets had become the cradle of interplanetary commerce and the ancient Martian civilization thrived, a startling discovery shattered the status quo—a mysterious tenth planet, a rogue world from the depths of interstellar space. As it veered dangerously close to the Earth-Mars spaceways, it threw astronautic calculations into disarray and ignited chaos on both inhabited worlds. Little did they know, this was no ordinary celestial body. It was WANDL THE INVADER, a vibrant world inhabited by formidable minds and terrifying creatures, arriving with intentions far beyond mere astronomical coincidence! - Summary by Original Gutenberg text