SCP Foundation

So you're aiming for sentient, but not sapient, sort of like bacteria?

Yes. I planned for the smog to contain an unknown pathogen that has striking similarities to extraterrestrial ones. It would appear to only react to its environment anything beyond that I haven't really considered much.

This doesn't appear to serve any purpose whatsoever other than making the smog creature scary. Typically when designing scary living creatures, their effects aren't designed to make them scary, but are rather designed to help them survive, with the added consequence of being scary. Also, these effects kind of put it in the "generic makes-you-go-crazy object/creature" category.

While that is true in one sense I had planned for it to be more the reason behind Jack's behavior and less about it being scary. It would be a cause and effect system where Jack was just a victim to the smog's nature. Yeah, I was thinking on this right after I made this thread. A new idea that came to me was that the smog pathogen could feed off some sort of chemicals/reactions in the brain from stimulus. Yeah, I thought that as well.

This seems like a good starting point for some backstory, I suggest you expand a little on that.

Overall, I could definitely see this idea being really good, but I feel the one thing that it needs is some sort of story. Perhaps make it somehow connected to Jack the Ripper's consciousness, and make it continue his serial killings.

Well, glad to hear that. I was unsure how it would be received. I have an idea for a Tale already that will establish a large majority of its history. Possibly dealing with the Great Fire of London in 1666. As for connecting it to his consciousness I think that would void a few concepts I've already established and would like to keep. Mainly being it's of extraterrestrial origin and is a organism of instinct not thought, at least beyond basic perception and reaction to its surroundings and stimulus. I would also need to establish a motive as to why it would continue his killings. Which would most likely need to relate to survival or benefit of some kind. Regardless, thanks for the suggestion I'll keep it for later consideration.