The Emerald Hounds were originally discovered and named by settlers on Emeralis Prime in the 63rd century. It was not long after they were discovered that a great evolutionary movement occurred that turned the Hounds into a bipedal war-like race. For the next century, the species constantly fought against the Galactic Alliance, the Shadow Proclamation, and Earth's Special Forces. Near the turn of the 65th century, a political and philosophical movement started on Emeralis Prime known as "the Awakening", which resulted in the Hounds as a race as a whole becoming a very peaceful one.
Emerald Hounds, originally, appeared as very large dogs with a green sheen to their fur. When they evolved into a bipedal species, they retained this trait, as well as gaining an oracular green glow to their eyes. They are generally well-muscled and athletic in body shape, all four of their limbs set off by sharp claws.
A group of Emerald Hounds led by Voganru were exiled from Emeralis Prime in the 67th century by the Emeralis Presidium and were sent back in time and left stranded on Earth in the 17th century. In the city of Verona, Italy, they established a base of operations as they attempted to drain the energy from humans in order to power a ship to escape "primitive" Earth. It was because of this that they came into conflict with the Tenth Doctor, who gave them one opportunity to stop and even offered them help. When they refused, he sabotaged their ship's engines, causing them to overload and explode, killing the exiles.