Neutron eater

The neutron eaters were mysterious entities, one of which was accidentally released by CERN's Large Hadron Collider.

Biology
The neutron eaters fed on the neutrons found in normal matter. This diet would sicken and weaken humans who were fed on it, reducing their density and causing them to give off an unusual glow. If the neutron eater was destroyed, the neutrons would be returned, instantly healing the victim.

The neutron eaters attracted their prey using psychic powers. They would impersonate the dead, mimicking their voices and citing events which they found in the victim's memory. (BBCR: Lost Souls)

History
When CERN's Large Hadron Collider was switched on for the first time, a portal was opened to another reality. Though it was only switched on for a few nanoseconds, a neutron eater was able to escape into the universe. It eventually met Oliver Harrington and was able to convince him that it was his dead wife Marie. Oliver hid the bodies of the victims of the neutron eater, convinced that they were turning into angels and that they would soon be returned to Heaven.

When UNIT came for the official unveiling of the Large Hadron Collider, Martha Jones discovered that people had gone missing. She contacted Torchwood and convinced them to help her investigate. Eventually, they linked the disappearances to the tunnels of the Hadron Collider, and Ianto Jones and Gwen Cooper went to investigate. Ianto eventually encountered the neutron eater, who convinced Ianto that it was Lisa Hallett and then fed on him. Gwen then tried to escape with Ianto, with the neutron eater attempting unsuccessfully to trick her. In the meantime, Jack Harkness was attempting to convince Professor Johnson to shut down the machine, since it would open another portal and release more neutron eaters. Jack also attempted to make Oliver believe that the neutron eater was dangerous, but Oliver didn't believe him and went to confront the neutron eater in the tunnels. Oliver and the neutron eater were both trapped in the tunnels and were destroyed when the machine was modified to stop the portal from opening.

When Jack Harkness was still with the Time Agency, he found the remains of another encounter with a neutron eater, which had devastated a colony. (BBCR: Lost Souls)


 * When and where this occurred in unknown, but it probably was an Earth colony planet.