The ships hummed as they descended through the blue green planet's atmosphere.
In preparation for colonization this world's dominant species had been exterminated by an engineered organism. The plan was simple. The dead of the target species are infected, reanimating them and giving them a craving for living flesh. They attack the living, killing and infecting them. Humanity was converted in weeks.
The ships landed and the colonists looked out on an empty planet. Everything was silent except for some bird calls. Emboldened by their success, the giant brains left the safety of their crafts to explore their new home.