Just what was the weapon used by the Mistress to kill off the unfortunate Dr Chang after telling him to ' say something nice' & positively relishing his fear - an upgraded TCE ( Tissue Compression Eliminator), as her first & second incarnations favoured...
...or a variation on her sixth self's laser screwdriver?
Unsurprisingly the first appearance of the TCE came alongside its wielder in Terror Of The Autons- it worked by shrinking its victims to almost doll-like size, with the shrunken bodies of its victims often left for the Doctor to find as a Masterly calling card via matter condensation!
Following its début, it would not appear on screen again until The Deadly Assassin...
After a cameo in Mark Gatiss's Last Of The Gaderene as part of ' Inspector Le Maitre's ( French for ' The Master')'s plans to assist the titular Gaderene in an invasion of Earth while assuming the alias of an officer from Scotland Yard, by which time the death of Roger Delgado necessitated a regeneration- the transitional 'decaying/burnt Master' portrayed by Peter Pratt. No explanation for the change was given until John Peel's Eighth Doctor Adventures novel Legacy Of The Daleks, which finds the Delgado Master, fresh from the events of Frontier In Space - using the alias 'Estro', Esperanto for ' Master'- attempting to assist Lord Haldoran in making a bid for power on 22nd century Earth, which is still dealing with the after-effects of the Dalek invasion witnessed by the First Doctor thirty years after the event.
The Eighth Doctor at this point has also seen his Third self gain the TCE following a brawl after a surprise attack on UNIT HQ by the Master, after which the furious younger Doctor nearly attacks his newest self with the weapon before giving it to him, part of the process of regaining his past memories in The Eight Doctors- he'll later use it on a spider from Metebelis Three to help his Seventh self out of a tight squeeze.
Susan Foreman-Campbell is still where he left her way back then, now married to David Campbell- the young man she fell for. It would seem she, as well as the Doctor's newest companion Samantha Jones ( this being only the tenth novel in the series) is missing...& its partly thanks to her that the Master ends up nearly burnt to a crisp! Attacking him with both his own weapon ( the TCE) & his TARDIS' telepathic circuits, she succeeds in frying him to within an inch of his life & ensuring he ends up on Tersurus- where he'll later be found by Chancellor Goth just in time for The Deadly Assassin..........
He even manages to speak a little of the language from which he's drawn his latest alias- "Doktoro, Mi ĝojas ke vi estas tiu kiun mi bezonis por kompletigi la ludon." translates into English as "Doctor, I am so happy, you are the one I needed to complete the game."
After he gains a new body from Tremas, the TCE is used again in Logopolis, during which of course he shoves the Fourth Doctor off a radio telescope- causing his regeneration. Not wanting to waste any time in the aftermath, he & his trusty weapon, which now appears to be able to completely disintegrate its targets, just as 'Missy's' weapon is shown to be able to, appear once more in Castrovalva - this time he's using the alias of 'the Portreeve'. You might also remember ' Kalid' from Time-Flight!, during which its used once more.
And he's not finished with it yet! Its in 'Sir Giles Estram's arsenal during The King's Demons & again in the 20th anniversary special The Five Doctors. Next he'll be off to Sarn for Planet Of Fire with it as he seeks to use Numismaton gas for his own ends, to return himself to normal size after accidentally shrinking himself with the TCE, leading to a final meeting with the Fifth Doctor.
Killingworth is our next stop, the Master working with the Rani during the Industrial Revolution in The Mark Of The Rani. Its final bow arrives in The Ultimate Foe, making way for a replacement by the time his future self is Prime Minister of Great Britain having caused quite a list of deaths, which includes Goodge ( from Terror Of The Autons), Commander Hilred & Runcible's unnamed assistant from The Deadly Assassin, a police constable & Tegan Jovanka's Aunt Vanessa ( Logopolis) & a hapless miner & his dog in The Mark Of The Rani.
Taking inspiration from the Doctor's sonic, ' Harold Saxon'- the alias, along with his Prime Ministerly title, serving as a clever anagram for ' Master No. Six' ( John Simm being the sixth man to play the role on television) builds a laser variant! First seen in The Sound Of Drums/ Last Of The Time Lords, among its functions is a form of the age-regression technology developed by Professor Lazarus, which he uses on the Doctor. "Laser screwdriver. Who'd have sonic?" indeed?
His political career was quick to gain momentum- he was Minister of Defence by December 2007, & it was he who gave the order to bring down the Empress of the Racnoss. Around the time of Love & Monsters his campaign to become Prime Minister was well under way. How did he win power so quickly, just a year after that? Simple- the Archangel Network, which broadcast a hypnotic signal encouraging the population to vote for him! To those who heard it, it sounded exactly like the drumbeat the Master had stuck in his head).
It was he who funded Lazarus's experiments, with a view to refining them for use within the aforementioned laser screwdriver. Announcing a belief in the existence of alien life, he then claimed to have made ' first contact' with the Toclafane, actually the cannibalised remains of the future of humanity as he'd encountered during his previous incarnation as the Chameleon Arch-aided Professor Yana.
Ordering the deaths of one-tenth of the human race, work began on his 'New Time Lord Empire'.......then he died, seemingly at the hands of his own ' wife', Lucy before being resurrected & sending the Time Lords back into the Time War after learning of Rassilon's part in placing the drumbeat that drove him insane into his mind.
Which brings things nicely up to date- what with his recent gender swap & change of name!
So, I think The Mistress's weapon could be another variation on the TCE, myself. But only Steven Moffat knows the truth.
What do you think?