Time Manipulator

A Time Manipulator was a time device that, if created, could alter time on a grand scale.

The Rani's plot
The Rani's plot to create a Time Manipulator had several distinct parts...
 * the intellects of several geniuses from across time and space, including the Doctor's, merged into a giant Time Brain.
 * building a launch pad on Lakertya with a fixed trajectory matching the solstice of a strange matter asteroid.
 * the Brain creating/finding/synthesizing a lightweight substitute for strange matter.

With accidental assistance from the Doctor, the Time Brain had found a good substitute for strange matter: Loyhargil. It then produced the Loyhargil and loaded it into a rocket, as strange matter could only be detonated by strange matter, or the substitute of Loyhargil.

Upon detonation, the strange matter explosion would result in the generation of helium 2 in the form of a supernova. The helium 2 would then fuse with the upper atmosphere of Lakertya, creating a thin shell of chronons. In the same milisecond, the cortex of the Brain would become active and grow until the space between shell and planet was filled.

With this "monstrosity," as the Doctor called it, the Rani would be able to change the order of creation. Returning in her TARDIS after the turmoil had subsided, she would use the Manipulator to alter the history of the universe, such as helping the dinosaurs of Earth to reach their full potential, eradicating humanity in the process. (DW: Time and the Rani)