M is for... Mentors

The Mentors are the amphibious inhabitants of the planet Thoros Beta. Legless, green-skinned, slug-like creatures, they thrive on money-making and profit. For them, the worst thing that can ever happen is poverty. Their financial skills led to them being employed by a number of intergalactic businesses. When the Doctor first met the Mentor Sil, he was representing the Galatron Mining Corporation. This organisation was reaping the benefits of an exclusive deal with the planet Varos for the mineral rights of its Zeiton 7 ore. This was essential for time warp engineering. Sil and his company had bribed the Chief Officer of Varos to ensure that a generation of Governors accepted low payment for the ore - far below its true worth had it been sold on the open market. Harsh conditions on the planet would be blamed on the Governors, and any attempt to rebel against the Corporation would lead to an armed invasion of the planet. During his visit to Varos, Sil saw the potential for marketing the various punishments which its government inflicted on its wrong-doers.

The Doctor was able to convince the current Governor of the ore's true worth. before Sil could call in an invasion force, a second source of Zeiton 7 was found - one out-with control of Galatron, so they ordered Sil to start paying whatever was asked. Sil doubly lost out, as the "video-nasties" side-line was discontinued by the new regime.

On their homeworld, the mentors were led by Lord Kiv, who had a particular aptitude for financial matters. He decided which schemes should be invested in and which should be avoided, as his great mind could foresee potential profit or loss which his underlings might not envisage. One of his rules was that there should be no speculation. Investment had to have a sound basis. 

His existence was threatened, however, by the physical increase in his brain. His skull could no longer accommodate it. Sil was tasked with locating and employing a physician who would be able to save Kiv's life - under penalty of death to both him and the doctor if they failed.

A discredited Earth scientist named Crozier was given the job and he came to Thoros Beta to experiment on potential brain transplanting techniques. The humanoid inhabitants of twin planet Thoros Alpha had long been enslaved by the Mentors, and many of them were shipped to Beta to be experimented upon. The Doctor and companion Peri arrived on the planet after he had begun investigating the sale of advanced weaponry to a number of alien kingdoms such as the Krontep. Their king, Yrcanos, was prisoner on Thoros Beta, where Crozier was attempting to permanently pacify his mind. The Doctor had his mind scrambled by Crozier when he used his equipment to interrogate him, and for a time he appeared to join forces with Sil. The Mentor saw the benefits of having a Time Lord ally, as he could inform of future events without resort to speculation.

Initially Crozier planned to transplant Kiv's brain into a new skull - selecting as a temporary host the body of a more primitive ocean-going Thoros Betan, which still retained its toxic sting in its tail. This had brown skin rather than green.

Knowing that this could only ever be a temporary measure, Crozier looked to his mind-altering technology and realised that he could transplant the mind of Kiv, rather then the physical brain. The subject chosen was Peri. The Time Lords were aware of the scientist and his work, and realised that it would cause chaos throughout the cosmos as no-one would ever die if they could simply transplant their minds into new bodies. They elected to manipulate Yrcanos, turning him into an assassin. The Doctor had already initiated a revolt on the planet by destroying the mind control equipment which subjugated the Alphans. He was dragged away by the Time Lords whilst Yrcanos was left to kill Kiv - now in Peri's body - Sil and Crozier. It later transpired that the assassination had been faked by the Valeyard at the Doctor's trial. Peri had survived - suggesting that the operation on Kiv had never taken place or had failed. The true fate of Sil and Kiv is therefore unknown.

Played by: Nabil Shaban (Sil), Christopher Ryan (Kiv), Richard Henry. Appearances: Vengeance on Varos (1985), Trial of a Time Lord Parts 5 - 8 aka Mindwarp (1986).

• Deep Roy also played a Mentor, uncredited, in Mindwarp, as well as portraying the Posicarian ambassador.
• Shaban's costume changes considerably between his two appearances. The first had too rigid a headpiece, resulting in his face becoming detached from its surround in some scenes. The second version was more lightweight and fitted better to the facial make-up. He's brown in Varos and green in Mindwarp, but some amphibians do change colour.
• Whilst Shaban's disability allowed him to fit into his constrictive costume, Chris Ryan had to either have his legs strapped up underneath him, or have them fit through a hole in whatever he was sitting on.
• Philip Martin had originally hoped to have Sil actually sitting in his tank of water, as he knew very few water-based creatures had appeared in the series. The practicalities of the costume and studio filming led to Sil simply sitting on top of the tank.
• Sil's odd speech patterns are supposed to be due to his faulty translator, but he also speaks this way at home with Kiv.
• The marsh-minnows Sil eats were actually peaches, dyed with green food colouring. They gave Shaban the runs.
• Sil has made one further appearance, in an unofficial spin-off video called Sil and the Devil Seeds of Arodor (2019). This also features Chris Ryan as Kiv, but here he's in a humanoid body.