M is for... Melkur

The bio-electronic Source which influenced all life in the Traken Union had the power to immobilise threats as soon as they arrived on any of its worlds. Any creature which harboured evil intent was immediately petrified, its body eventually crumbling to dust. Such creatures were known as "Melkur", which meant "a fly trapped in amber". A young noble of the Traken court would be tasked with tending the Melkur until it had disintegrated.

One particular Melkur had arrived in the grove outside the main Consular chambers on Traken, and a girl named Kassia was given the role of looking after it. She took her duties very seriously, becoming quite obsessive about it. It was noted that this creature did not deteriorate like the others, suggesting a more intense level of evil whilst it still thrived. Eventually  Kassia grew to womanhood and was to be married to her fellow Consul Tremas. Responsibility for the Melkur was to pass to his daughter Nyssa, but Kassia proved to be possessive of it. 

It began to communicate with her, urging her to follow its advice. It vowed to prevent Tremas from being taken away from her, as he was going to become the next Keeper. It began to secretly move around the grove, and on the night that the Doctor and Adric arrived it killed one of the local Fosters and attacked the Keeper.

The next day it caused the TARDIS to disappear, hidden in a pocket of time. The Doctor took some energy readings which Adric later noted resembled the signature of a TARDIS - for that was indeed what it was. 

The Melkur manipulated Kassia into taking on the Keepership herself, only to see the Source consume her as it took her place. Within was the Master, the Melkur his disguised TARDIS. He planned to usurp the Keepership so that the Source would repair and prolong his existence.

The Doctor arranged for the Source to reject the Melkur, destroying it - but the Master had a second TARDIS hidden onboard and used it to escape.

Some time later, Nyssa was confronted by a mental image of the Melkur - an attempt by the Master to stop her interfering in his schemes on prehistoric Earth.

Voiced by: Geoffrey Beevers. Played by: Graham Cole. Appearances: The Keeper of Traken (1981).

• Beevers was the husband of ex-companion actor Caroline John (Dr Liz Shaw) and had previously appeared in one of her stories as a UNIT soldier (The Ambassadors of Death). He was credited as Melkur to disguise the fact that he was really playing the Master.
• Cole is best known for his long-running role as PC Tony Stamp in The Bill, but at this time was a regular background artist and monster performer in Doctor Who. He also operated the Melkur in its cameo appearance in Time-Flight.

• The design of the Melkur was inspired by the 1913 bronze statuette titled "Unique Forms of Continuity in Space", by artist Umberto Buccioni. It can be seen at Tate Modern in London.

• The Melkur prop as it appeared at the Doctor Who Experience in Cardiff in 2012 and 2017: