A suggestion to put before all others, in my admittedly not very humble opinion:
Just Do It!!!!
For some people, making that first submission can be daunting. Having people looking over and judging your work can cause anxiety, which might keep you from posting it.
Just Do It! Ignore the voice that says no, and share your ideas. Don't be afraid of honest criticism. Follow all the other advice to make it the best you can, but remember the old saying "Perfect is the enemy of Good." Do your best and then GET THAT SUB OUT THERE! Go to Comment
This is one 100 word challenge which I think would have had much more potential expanded.- at the moment it just appears to be a general thrown potion which will cause weakness and possible blindness, and perhaps suffocation.
I get the feeling that you are maybe trying to suggest that the goop is somewhat sentient/intelligent and will intentionally soak anything it's thrown at, but i feel it's not explained enough in the post.
I'd like to know where the goop came from: Is it a tar-like chemical mixture? Is it a stoppered sludge-creature? Is is a mixture of herbs/reagents?
The Vile Vial is a cool name, however! I know it defeats the purpose of the 100-word post, but more info would be awesome. Go to Comment
Now see, i read the name (great name) and figured the vial *itself* would be vile. In other words, an evil, sentient glass container that can either corrupt whichever liquid (magical or otherwise) is placed inside, or worse yet, it doesn't mater whats inside! You can throw the vile vial at a fleshy opponent, and upon breaking, the glass shards worm their way and "crawl" deep inside flesh, severing arteries and causing great damage otherwise. Later, the glass shards seek each other out again, and re-form the glass vial, complete with evil sentience again. Go to Comment