Cancer

[Ashe]

Its an interesting idea, and one that has applied to numerous other situations. I think the problem would be preventing the helpful cancer from mutating further, especially when its already been pushed to be able to do that, and hope you don't get double cancer OR this cancer starts losing track of what exactly its supposed to feed on. Cancer is so varied as well that its hard to trust something like that.

I don't even think it works that way though. To my understanding, there is no "feeding" type thing, its just that they corrupt what's near it, and then that corrupts what's near it, by screwing up the chemicals for whatever the cells need.