The Void Ship, also known by its not-so-technical term, the sphere, was an extremely advanced spacecraft designed to traverse the Void, which was the emptiness that existed "between" all parallel universes and all different dimensions. Void ships were considered by the Time Lords, including the Tenth Doctor, to be impossible to build and strictly theoretical. The Doctor understood enough of the principles to explain how the Void Ship worked. However, one was created by the four elite Daleks known as the Cult of Skaro during the Last Great Time War. Their featureless metallic spheroid was the only known example in history of such a vessel. (TV: Doomsday)
When travelling through the Void, the ship was separate from time and space, which may explain why, until activated. The Void Ship could protect its occupants from the Big Bang, the end of the universe and the start of the next one and it wouldn't be affected. It defied all forms of analysis, meaning it had no detectable mass, heat, quantifiable age or radiation, though it could be visible at the specific location where it was chosen to eventually emerge. Due to these properties, people who looked upon it found it deeply unsettling; foreboding. An invisible barrier prevented anything from having physical contact with the ship, at least while it wasn't active. (TV: Army of Ghosts)
During the Time War, four elite Daleks were selected (PROSE: Birth of a Legend) in secret by the Dalek Empire to constitute a group known as the Cult of Skaro. The Cult was "above and beyond the Emperor himself" and considered merely a legend by the Time Lords. They correctly predicted that the Time War would result in complete disaster for the Empire, and created the Void Ship to avoid the impending destruction, where they waited in the Void for the War to conclude. These four Daleks also stole a Time Lord prison ship containing millions of Dalek prisoners (designated the Genesis Ark). (TV: Doomsday)
Inside the Void Ship, the four Daleks worked to open the Genesis Ark and free their imprisoned comrades. As they came closer to their goal, the Void Ship began to create spatial disturbances at a location above the ground in Canary Wharf, London, sometime prior to 2005 (AUDIO: One Rule). Perplexed scientists (led by lab doctor Rajesh Singh) and officials (led by Yvonne Hartman) working for the Torchwood Institute built a skyscraper, Torchwood Tower, to secretly study the disturbance. Eventually the Void Ship became visible, but untouchable. It created an atmosphere of foreboding around it.
The Void Ship created a "wake" which connected the universe to an adjacent parallel universe that Tenth Doctor would label "Pete's World". Unknown to the Daleks, their Void Ship's wake created an entry point for an army of Cybermen native to Pete's World. The staff of Torchwood 1 ignored the Doctor's warnings, and unintentionally paved the road for the Cybermen to invade. The Cyber-Leader increased the Ghost Shift to 100%.
The "ghosts" were an army of Cybermen and they took control and were prepared to upgrade the population after escaping Pete's World. The same day, the Void Ship opened, and the Cult emerged with the Genesis Ark. They were prepared to destroy the Sun to force open the Ark. Before they could do so, Mickey Smith accidentally transferred his artron energy to the Ark when, as a reflex, he put out his hand for balance when a Cyberman shoved him against it, allowing it to open as the Time Lords' intended. During the subsequent Battle of Canary Wharf, as the freed Daleks began to exterminate the Cybermen, the Doctor and Rose Tyler reversed the rift. The Cybermen, virtually all the Daleks, and presumably the Void Ship itself, were forced back into the Void. (TV: Doomsday)