Sex Gas is a type of intelligent gas, one of which came to Earth in an meteorite which fell near Cardiff and possessed a local girl named Carys Fletcher. The gas on Earth found that the energy produced during sex was the best. This sex is fatal for the other participant, since they will be disintegrated and absorbed at the climax.
- The Cardiff rift may have attracted the meteorite in some way.
In its natural form, the sex gas is a thick purple gas with high quantities of vorax and ceranium which can move about at will. It can't survive in the atmosphere of Earth for very long and will quickly turn into a pink powder.
In order to survive, the gas enters another organism through the mouth and nostrils. While inside a Human or a rat, the sex gas causes a variety of changes, both mental and physical. The host gains an enormous sex drive, sharing in the gas's addiction. Despite its need to absorb the energy produced by heterosexual sex, it had no objection to homosexual sex. The host will develop special pheromones which are irresistible for other members of the species of either gender. Internally, the heart and brain will increase in size and the lungs will shrink, which will eventually explode and kill the host. (TW: Day One)