Zolfa-Thuran

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.

Biology
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)

Though not extremely mobile in there natural form, but does seem to be able to slither along the ground. When doing this, there spines presumably retract, causing him to appear more like a green slug.

Technology
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)

History
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)