Well, virus are already like poisons so why not develop the real deal? Its in the field of chemistry of course. These poisions can be natural (Found in some corner, badlands, sewers, or just somewhere with hazzardous atmostphere or something.) And the designer posions with designer antidote. Isnt it awesome to kill an entire populi with it? Not that I plan to. Lol XD Anyway, just a share of idea, still it's awesome to have poisons, really have varous of uses In game.