Toclafane

The Toclafane were fairy tale monsters from Gallifrey, their name, like the Bogeymen on Earth, just made up.

In 2008, the Master claimed to have contacted the Toclafane (in reality a race of robotic beings) and, using a paradox machine linked to the Doctor's TARDIS, allowed the enture race to pour through to decimate the Human population and create a Time Lord Empire. (DW: The Sound of Drums / Last of the Time Lords)