Prophecy was the name given to a Poldagon scientific facility that could change itself into other planets. It was given this name by the Seventh Doctor in memory of a clone of Michel de Nostradamus. In its natural form, its surface looked like a grey sea.
The planet was created by the Poldagon out of bio-matter. Using scans of the hundreds of planets they had encountered, they formed the bio-matter into simulations of the planets.
An incarnation of the Doctor visited the planet while it was a simulation of Celdor. He left the planet thinking that it was Celdor.
When the Seventh Doctor wanted to go to Celdor again, he landed on the planet while it was in the form of Earth in 1560. The planet was put in this form to let the Kro practice invading a primitive planet. However, at this time the Poldagon began losing control of the bio-matter. One of the simulations of people that inhabited the fake world gained sentience. The Doctor helped this fake Nostradamus get both the Kro and the Polgan off the planet and the bio-matter was left to create its own civilisation. (AUDIO: The Doomsday Quatrain)