Original: From the depths of outer space, an asteroid of vast proportions carried an alien smog who when inhaled, k!lled the poor bugs who breathed it in, as their lungs steadily lost function. As the bugs of this world scurried to find a cure, the Arachnids managed to find one that worked, but only on themselves. It granted them hallucinations however, and small powers. The other bugs, ever so prideful, considered this a betrayal by the Arachnids. After an eradication of the arachnid populations, they came together to make their own cure, using steam powered factories and machines to do their bidding. However, this backfired terribly, as the sentient smog took over these machines and used it against the insect population. Now, our protagonist who just so conveniently happens to be immune to this smog, is wandering around trying to stop the chaos in any way he can.
Better version: A vast and sentient alien smog billowed from the depths of a fallen machine of the insects. This horribly vast hivemind creature had been extracted from the heated rocks of the fallen meteorite only days before. During its capture, it only continued its escape. Once it succeeded, he1! broke loose. The insects and bugs of all kind scurried to find some cure to this problem. A solution of any kind would do. The Arachnids were first, their cure a tainted and changed version of the smog, that did not kill, but still granted hallucinations and sometimes even small minor powers. It had been engineered to only work on Arachnids however, and other insects were furious. A great battle erupted, causing many deaths, and the smog to rise in strength and power. The arachnids had been eradicated, and the remnants scattered. The insects over the years continued to fabricate machines and factories, powered by steam. That evil corruption, the smog, corrupted these machines, rendering them enemies. As insects failed to defend against their own creations, a lone unknowing spider rises out of the darkness. While not immune to the smog, it carries a weak vaccine of it. This vaccine has been able to protect it from and repel the smog, but does not grant the fantastical visions and powers of the arachnid cure. It only knows that it needs to end this smog once and for all, no matter the cost.