Death Wheel

The Death Wheel was a Dalek ship built in the orbit of the planet Hell during the Second Dalek War of the 26th century. The Death Wheel was a doomsday weapon instrumental to Operation Genocide, overseen by the Emperor Dalek himself.

History
The Daleks occupied Hell and constructed the Death Wheel in orbit. They set the enslaved Helkans to work mining deadly helkogen gas that was transported to the Death Wheel in vast quantities by cargo ships. The Daleks intended to release the gas above the planet and cause the extinction of all living things below.

The Seventh Doctor and Abslom Daak infiltrated the Death Wheel after learning the Daleks intended to gas the planet. After fighting their way out of captivity and assessing the layout of the ship, Daak prepared to sacrifice his life to destroy the Death Wheel, flying a Dalek hoverbout straight into the reactor core. (COMIC: Nemesis of the Daleks)

Though the Death Wheel was destroyed, Daak survived after future Daleks extracted him via transmat moments before his death, so he could help track down the Doctor in a bid to locate Davros. (COMIC: Emperor of the Daleks!)