Through the Monk's Gallifreyan technology, they were able to project a time shield that became the source of parallel realities. The purpose of this shield which was located in the Arctic on Earth was to protect the Ice Warriors operations in 1963. Using their mothership which had established a base in the region, they created a shaft down to the planet's core where they began dropping super heated silica which was to cool the Earth's molten centre. The aim was the creation of huge crystals that were to be used as weapon components for the Ice Warriors in order to create sonic cannons capable of erasing whole continents.
The Fifth Doctor, however, discovered this event and together with a special team of human soldiers called SAG 3, they were able to storm Autek's base. With his headquarters overrun and his soldiers fighting the enemy, Autek ordered the mothership to lift off where its engines killed most of the Ice Warriors whilst their leader himself fled with the Monk in his TARDIS. (COMIC: 4-Dimensional Vistas)