Vervoid

Vervoids were a type of artificially created humanoid plant. Created as a slave species by scientists, the Vervoids pined for freedom and eventually decided to destroy their human oppressors. The happenings that followed this were used as evidence against the Sixth Doctor when he was on trial.

Biology
Vervoids were the size of humans, with pink, head-like organs surrounded by petals. They could release swamp gas out of their mouth-like appendage when panicked. They had short tendrils at the ends of their "arms", which served as hands for simple tasks or to shoot poisonous darts. They were covered in maple-like leaves, capable of regenerating into entire Vervoids if placed in soil. Vervoids grew in pods which were awoken when exposed to a higher spectrum of light. Vervoids had short lifespans, living for less than a year before decaying. (TV: Terror of the Vervoids)

History
Vervoids were created by a team on Mogar as a race of slaves. This attempt was not entirely successful, as one of the team members was infected by Vervoid pollen and began to mutate. The Vervoids themselves were genetically inclined towards survival. Instead of serving the humans, they saw them as a threat.

After an accident on the Hyperion III in 2986, the Vervoids were awakened early and attempted to kill all humans. The Sixth Doctor stopped them by speeding their growth rate with vionesium, accelerating their rate of photosynthesis and causing them to die from old age.

Previously, the Doctor's trial had viewed these future events but the evidence had been tampered with by the Valeyard, prompting him to add genocide to the Doctor's crimes. The Doctor did not deny wiping out the Vervoids, but maintained he had no other option to save the lives of those whom they were attacking. The charge was ultimately not pursued by the tribunal, due to other extenuating circumstances. (TV: Terror of the Vervoids).

When visiting his past self during his trial, the Eighth Doctor argued that the charge of genocide was ridiculous as the Vervoids were an artificial creation and therefore not covered by Article 7. (PROSE: The Eight Doctors)

Some time between the end of the trial and the Doctor's first meeting with Melanie Bush in his personal timeline (and therefore before the genocide of the Vervoids), the Doctor, Jason and Crystal visited the Bar Galactica in their search for a missing US Peace Envoy. A Vervoid was among the bar's customers. (AUDIO: The Ultimate Adventure) In the early 27th century, there was a popular television series called Only Fools and Vervoids. (PROSE: ...Be Forgot)

Behind the scenes
Tom MacRae, writer of The Girl Who Waited, said that one of the scariest Doctor Who moments for him personally was a scene in Terror of the Vervoids where Vervoids attacked a man using deadly seed pods delivered from their hands. He speculated that the idea of hands being frightening may have subconsciously inclined him to create the Handbots, who appeared in his story.