Went to Cistern of slaughter and after killing about 20 skags I got no progress towards the challenge
I had the same issue but, for whatever reason, I found that the service bots just east of Casa de Timothy in the Spendopticon map do count.
I think it’s because it’s not counting other dlcs(just in case some people don’t have it). I can confirm that bots on Killavolt map do count. If you go along the left side of the map there’s 6-8 of them every time.
I believe it means kill 300 creatures that originated from Promethea like Ratches (which can be found on other planets), like Saurians originated from Eden 6, skags from Pandora etc.
Yes. I got it by killing ratches in voracious canopy. I just wish they would be more clear about it