The Zolfa-Thurans were an intelligent cactus-like species who were the original inhabitants of the planet Zolfa-Thura. The last survivor of the race, Meglos, impersonated the Fourth Doctor in an attempt to steal a Zolfa-Thuran energy source called the Dodecahedron.
The Zolfa-Thurans were normally immobile, cactus-like plants reaching around 1.5 metres tall. They seemed to have telepathic powers which allowed them to be very perceptive and allowed them to communicate with other life-forms. (TV: Meglos)
The Zolfa-Thurans had access to very advanced technology. One of the more unusual devices turned the target into energy. While they were in the energy form, they could possess a humanoid and could then interact with their environment. They could also change the appearance of the possessed humanoid, but only to a similarly shaped being. As well, the host took a more cactus-like appearance over time.
Another major technological development was the Dodecahedron. The Dodecahedron could produce enough energy to power the galaxy or a galaxy-spanning weapon. The Dodecahedron was being used by the Tigellans to power their city. (TV: Meglos)
Soon after the creation of the Dodecahedron, the Zolfa-Thurans went to war to stop the use of this enormous power-source. At the end of this war, the entire planet was ravaged; this was caused by the Zolfa-Thurans creating the Screens of Zolfa-Thura. This device would be powered by the Dodecahedron to destroy Tigella. However, a Tigellan agent shrunk the Dodecahedron, and took it to Tigella.
The Screens were activated, but with no Dodecahedron to power it, it caused a shockwave destroying all matter on Zolfa-Thura. Meglos, alone of the Zolfa-Thurans, who was locked in the base for crimes against Zolfa-Thurans, survived the war and tried to get back the Dodecahedron. Though he succeeded in obtaining it, Zolfa-Thura and everyone on it was destroyed due to the Fourth Doctor reverting the controls. This meant that the Dodecahedron destroyed Zolfa-Thura instead of Tigella. (TV: Meglos)