1.7.10 had some awesome "taint" mods such as my favorite, Cliffie's Goos [https://minecraft.curseforge.com/projects/cliffies-goos] however, none of these mods have been updated past 1.8.9 and i love the newer versions of minecraft.
I would love for someone to make a mod like these types of mods for the newer versions of minecraft. A block that can naturally spawn and slowly multiply to take over the world. Obviously a way to fight the taint would be good too lol
And yes, i know of the feature of thaumcraft that has taint however, i find that since it is only me and my husband playing, we have yet to see any taint actually appear and spread