Weed Creature
A weed creature was an intelligent, semi-mobile form of seaweed that once inhabited the Atlantic Ocean near the coasts of England. They were sighted by mariners as early as the 18th century, but the Seventh Doctor once described it as "primeval," existing since the days of the dinosaurs in Loch Ness. (PROSE: Christmas on a Rational Planet)
Weed creatures fed on gas and had stingers. A weed creature could also release poisonous gas or a foam that allowed it to mentally control those it touched, who in turn gained the ability to exhale gas. It was vulnerable to oxygen and high-pitched sound.
In the late 20th century, a weed creature was sucked up by a Euro Sea Gas rig. It enslaved Oak and Quill (and later John Robson and Van Lutyens) and used them to take over the refinery and rigs. It planned to conquer Earth, but was defeated by the Second Doctor, who used a recording of Victoria Waterfield's screams to destroy its nerve centre. (TV: Fury from the Deep)
