The Master's TARDIS (Death in Heaven)

After escaping Gomer's Asylum, (PROSE: Lords and Masters) escaped Gallifrey in a TARDIS. (TV: The Doctor Falls) It was a Type 45, (PROSE: Lords and Masters) like the Master's original TARDIS (PROSE: The Dark Path, COMIC: The One) which had been lost to a paradox during the Last Great Time War. (COMIC: Fast Asleep)

Some time after the Master escaped from Gallifrey, he flew his TARDIS too close to the event horizon of a black hole, blowing the dematerialisation circuit. He subsequently remained stranded on a decaying Mondasian colony ship for a number of years, until his future self,, was brought to the ship by the Twelfth Doctor in his own TARDIS. Due to a subconscious memory Missy had planted in the earlier Master's mind by terrifying him, she was carrying a spare dematerialisation circuit which she gave to the Master, allowing him to repair his TARDIS and leave, although not before she stabbed him, causing his regeneration into her. (TV: The Doctor Falls)

From his point of view, a younger version of the Twelfth Doctor had first become aware of this TARDIS's existence upon stumbling into the younger Missy's Nethersphere scheme in 21st century London. He guessed that she "must have a TARDIS somewhere", which she had used to upload all the dead of various eras of human history to the Nethersphere. (TV: Death in Heaven) After Gallifrey returned to the universe, (TV: Hell Bent) the Time Lords were able to track Missy through the link to the prime Eye of Harmony that powered the heart of her Type 45 TARDIS. After they tried to leverage this to have Missy carry out a mission for them, she fixed this weakness by jettisoning her Eye of Harmony and using an entrapped, experimental time-sensitive creature as a power source, instead. (PROSE: Lords and Masters)

When Missy went to investigate River Song at the Bekdel Institute, she escaped with the archaeologist to a Level 3 planet where the Time Lady made for the spaceport where she knew she could hitch a ride back to her TARDIS. (AUDIO: The Bekdel Test) However, Missy ultimately created a new, experimental "Master TARDIS" using her current TARDIS as well as the memory-wiped remains of her earlier, Mark 212 TARDIS. (AUDIO: The Belly of the Beast)

Behind the scenes
The official Doctor Who Twitter account reposted fan art by @roguerigatoni of the interior of Missy's TARDIS as part of #FanArtFriday. This is the only visual representation of this particular TARDIS to be properly acknowledged.