The Cold (Interference)

The Cold was two different substances; the skin of The Cold and the Cold itself.

The Skin of The Cold
Guest, Compassion and Kode sold The Cold as a weapon on Earth in 1996, which can remove subjects from the physical universe.

If a subject was introduced to The Cold they would be taken out of space and time and held in stasis with no ill effects to the subject.

Fitz Kreiner was sprayed with The Cold whilst in 1996, it wasn't until six hundred years later on the colony Ordifica that he was released.

The Cold itself
The Cold was believed by The Remote to be a loa, one of the spirits worshiped by the Faction Paradox.

However, it was actually a validium-based weapon which existed on the border between universes.

It had been seeping out through the centre of a giant Time Lord warship, upon which the Faction Paradox had situated a Remote colony; Anathema, on.