GURPS War Against the Chtorr (Steve Jackson Games)

What do the Worms Eat? Bushes. Trees. Dogs. Cows. Cars. And people. Especially people. The worms eat everything slower than they are. And the worms are very fast. The worms grow up to six feet long. No, ten. Twenty. Thirty . . . They just keep getting bigger and hungrier. They're the spearhead of an alien invasion . . . an ecological invasion. There seems to be no guiding intelligence - just thousands of different alien plants and animals, cooperating with each other as they destroy Terran species. More than half the world's population has fallen to alien diseases, and the rest are becoming worm food. So mankind unites against the threat . . . No, it doesn't. Earth's nations continue to struggle against each other, even as the aliens grow, and spread, and multiply, and eat. The world needs heroes. Or the world will be gone, turned into a screaming red jungle, a duplicate of the invading planet Chtorr.