Death Worlds are a classification of life-bearing planets. The chief difference is that the forces of nature are actively trying to extinguish life. The higher the number, the worse your planet is.
Earth rates a 4.5 on the Deathworld Scale, mostly because of Australia.
Class 1 Edit
The most common variety of Death World. One main hazard to evolving intelligent life. Usually in the form of hostile flora or fauna.
There is one Class 1 Death World that has none of the usual hazards, but does encounter regular bombardment by meteors. Once every two millennia, regular as clockwork.
Class 2 Edit
This type of Death World has two main hazards. One is usually weather phenomenon.
Class 3 Edit
Three kinds of threat to life. Flora, fauna and weather phenomenon are favourites, with geology as a close runner-up
Class 4 Edit
Four general threats to life. On these planets, you find unstable tectonics, furious weather phenomenon, toxic flora, toxic fauna, and a variety of predators.
Class 5 Edit
The entire planet is trying to kill everything on it, including everything on it trying to kill everything else. Nature red in tooth and claw. Life is nasty, brutish and short.
Class 6 Edit
Theoretical only. Not only is the entire planet trying to kill you, but the solar system is having a go at you too. You may be in orbit around a quasar or a black hole. Good luck. You're going to need it.