San Helios
San Helios was a planet in the Scorpion Nebula, on the other side of the universe from Earth. It once had an advanced civilisation with a population of 100 billion, and cities like San Helios City, but in the early 21st century it was ravaged by a swarm of Alien Stingrays, and all life on it devoured, turning the planet into a desert planet in less then a year.
After feeding off of San Helios, the stingrays attempted to open a wormhole to Earth, accidently trapping a group of humans on the planet in the process. The Doctor eventually re-routed the swarm to an uninhabited planet instead.
Before its demise, San Helios traded in "waste products" with the Tritovore race. As a result, a Tritovore crew was the first to discover the fall of the planet. (DW: Planet of the Dead)
- Interestingly, the similarly sounding Sanghelios is another fictional planet in the Halo series of games, from which the Elite race originates.
