Nemesis

The Nemesis, also known as the Statue of Nemesis and, upon the rocket-sled, the Comet Nemesis, was a statue of validium that was capable of great destruction.

Before arriving on Earth, the Nemesis had other forms that would horrify a person and had other names as well. It was also used by the Doctor once before, and only wanted her freedom. Since the statue was of validium, it could reform after it had been destroyed.

When the validium did arrive on Earth in Windsor in 1638, it was found by the evil Lady Peinforte who shaped it into a statue of herself holding a bow and arrow. Before she could use its power, the Doctor, knowing its power, launched it on the rocket-sled into space, without the bow and arrow. (DW: Silver Nemesis)