I am not 100% convinced that the slug Will coughed up was the same 'Dart' that we saw in the series. My guess is it got washed away to the water treatment / sewer. I wonder if that will play a part in the future, or if we are just to assume it became one of the many demodogs we saw.
Reading the wiki, apparently the pumpkin patch was where all the new demodog slugs were formed (not confirmed, but speculating): http://strangerthings.wikia.com/wiki/Slug-like_creature#Stage_One
The creators said they have a huge bible of everything about the Upside Down. I'd love to see what they've cooked up. I think we may have 2 more seasons left before they end the whole series, so I hope we get to know more about it, how it formed, what it actually is, the creatures, and so on.
Or I hope they'll release a book with all that information when the series ends.
Reading the wiki, apparently the pumpkin patch was where all the new demodog slugs were formed (not confirmed, but speculating): http://strangerthings.wikia.com/wiki/Slug-like_creature#Stage_One
The creators said they have a huge bible of everything about the Upside Down. I'd love to see what they've cooked up. I think we may have 2 more seasons left before they end the whole series, so I hope we get to know more about it, how it formed, what it actually is, the creatures, and so on.
Or I hope they'll release a book with all that information when the series ends.