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Meglos was a xerophyte, the last survivor of the Zolfa-Thurans. He was the last inhabitant of Zolfa-Thura and was cactus-like in appearance.
Meglos hired a group of Gaztak mercenaries, led by General Grugger and his aid, Brotadac, to bring him an Earthling. He was able to take on this human’s form. Meglos then trapped the Fourth Doctor and Romana in a time loop before taking on the former’s appearance. Disguised as The Doctor, Meglos had Grugger and his party take him to Tigella. He hoped to recover the Dodecahedron, a source of great power. Meglos shrank the Dodecahedron and then returned to Zolfa-Thura, where he began to activate it.
On Grugger’s request, he planned to destroy Tigella with it. However, the Gaztaks turned against him and locked him up. He was forced out of his body and re-entered his cactus-like form. The Doctor had meanwhile reverted the calculations for the Dodecahedron, causing it to destroy Zolfa-Thura and Meglos. (Meglos)
BEHIND THE SCENES
Gareth Roberts, the writer of the television story The Lodger, revealed in an interview in Doctor Who Magazine Issue 423 that he had planned to use Meglos in the story, but decided against it after similar-looking aliens, the Vinvocci, made an appearance in The End of Time. The magazine also showed an early draft of the script, which showed the meeting of the Eleventh Doctor and Meglos in which Meglos remembered The Doctor but The Doctor didn’t remember Meglos.
In an interview with Toby Hadoke in his Toby Hadoke’s Who’s Round podcast Crawford Logan revealed he voiced Meglos.