I've been playing through the Disharmony expansion and was gunning toward the "Cleansing the Galaxy" achievement. I was under the impression that all I had to do was to build Contamination Barriers on ten systems and the achievement would unlock. After doing this several different times on different saves, still no achievement pop.



Is this what "Purifying" a system entails? Or is there something else I'm missing.



Also, does anyone else have problems with the AI never building fighters or bombers? And how do you get collateral damage on troops?

I don't know the name of it, but it's the improvement that takes 5 turns to construct (it might be the one you mentioned, I'm not sure).



The game can actually be pretty weird with achievements; I still can't get the achievement for having a higher score than a Hard AI at turn 100, despite pulling it off a few times. If you really can't get the achievement, you should post it in the tech support forum.

That is correct all you need to do is build contamination barriers on 10 different systems. Make sure you end turn after these are built as it won't immediately happen. I gained this achievement using the current beta patch so maybe the version your using has the achievement bugged?