Hellflower

ONCE HE HAD BEEN A STAR MASTER--NOW HE DEALT IN SOUL-SHATTERING RUIN... Farradyne had committed the one unpardonable error a Space Master could make. He didn't die along with the other 32 passengers when his ship smashed into the Bog on Venus. They broke him--exiled him to the rotting fungus fields of Venus. Now his only desire in existence was to return to the cool, gleaning sea of deep space. And there was a way--only one. But he would have to become the vilest parasite in the universe--peddler of a poison that stripped the spirit, before it consumed the body... - Summary by back cover, Pyramid Books 1953 edition