The Vervoids were intelligent, mutant vegetal lifeforms created by Professor Lasky, Bruchner, and Doland on the planet Mogar. Vervoids appear as green humanoid leaf covered plant beings. Their pink heads flower from their necks and are surrounded by a yellow high "collar" of protective plant material.
As well as possessing intelligence, the Vervoids were capable of independent movement and could also speak and hear. Lasky planned to use the Vervoids to carry out mundane tasks which they would be able to undertake for little more than some light and food. The Vervoids, however, had other plans.
Vervoids were equipped with venomous stings and emitted poisonous marsh gas. Vervoid pollen was so powerful that even the tiniest fragment introduced to the human bloodstream would cause a person to become a hybrid Vervoid mutation.
The Vervoids were in pods and dormant when they were loaded onto the Hyperion III space liner, but were awakenened by an electrical light burst and hatched. Once free, they began a killing spree, using poisonous projectile thorns or exhaled methane gas, eventually they created a compost heap-like pile of dead humans. Their plan for taking over the ship was thwarted by the Doctor, who used vionesium light bursts to speed up their natural life-cycle. They all withered and died in seconds.
As these were the only Vervoids in existence the Doctor was charged with genocide by the Valeyard for this action.