The Eternines were a race that originated from the Eternium.
The Eternines could possess humans, and could remain dormant in their minds, allowing their hosts normal control. In their natural form, they appeared as globes of blue-white light.
When the Eternium was on the brink of death, the Eternines managed to open a pathway between the Eternium and the mainstream universe, allowing Watchlar to pass through. They manipulated aspiring poet Jared Malahyde by posing as humanity's ultimate evolved form, tricking him into arranging for the construction of the Utopian Engine, while he believed would bring the Eternines through to the present. In reality, the Engine would accelerate the age of all life on Earth so that this energy could be sent through to the Sternum.
Their first attempt was interrupted when the Eighth Doctor disrupted the machine so that it only aged all life on Earth forty years, and their second effort was averted when the Doctor linked the TARDIS to the Utopian Engine and used it to turn time back to before the Eternines even made contact with Malahyde. This erased the Eternines' contact with Malahyde, and the Doctor speculated that they lacked the energy to try and recruit someone else for their scheme. (PROSE: Reckless Engineering)