In a parallel universe, a version of the Master who was still Koschei travelled in a TARDIS with Ailla that eventually became stranded on Earth after it became irreparably damaged during a battle with a disembodied entity that used robots as its foot soldiers and tried to shroud the planet within a web-like substance.
Koschei and Ailla helped in the fight and managed to defeat the entity and its robots, but they were taken prisoner in the aftermath. The TARDIS was ruined, and the control console, which was the only part of it that was still intact, was cannibalised by the Republic of Great Britain.
When Earth was devastated beyond recovery by Eric Stahlmann's Inferno project at Eastchester, the Conclave learnt from video recordings that showed the Third Doctor's arrival into that universe from the prime universe that the TARDIS console could offer a means to save them.
They connected the TARDIS console to a nuclear reactor and used the console to send a travel capsule to the primary Earth where the survivors of the disaster would infiltrate positions of government and other positions. Their activities eventually caught the attention of UNIT, who enlisted the aid of the Master, because the Doctor and Jo Grant were not on Earth but on the planet Peladon, and former companions Barbara Wright and Ian Chesterton.
Barbara found the TARDIS console and believed for a moment that the Doctor was helping them before she remembered there were other TARDISes.
Koschei later told his counterpart that the only way to shut down the interdimensional corridor was to remove the TARDIS' main space-time element, which the Master did while noting that the console resembled the one he had used when he had travelled to his universe's version of Uxarieus. (PROSE: The Face of the Enemy)