At the foot of the wall, Nia dug for clams. The smooth gray jewels burrowed away from her probing toes. She scooped the sand fast with her hands before they could escape, then sifted the sea-soaked sand from the shells and dropped them, clattering, into the pail. Hot clam soup would make Mother feel better. They'd have to make do with the cream that the Marauders hadn't found.

Pail full, Nia walked back along the tide-line, the slow water surging over her feet. The sun had set behind the western mountain, and dusk turned the wall's smoky glass black. No one in the village of Summerset knew what dwelt on the other side of the wall. And no one dared to try traversing it. The gray glass reached high into the sparse clouds; it melded with the

I think there are a couple of places where you could trim this one-- She scooped the sand fast with her hands before they could escape, --might be better without the "fast". And for some reason I want to change turned the wall's smoky glass black to "turned the smoky glass of the wall black".

Anyway, I love the descriptions of the sand, beach, and even the way the clams sound when they hit the bucket.

What seems to muddy the waters though is that you've got three potential hooks going on here. 1) That the mother's sick. 2) Mauraders seem to have landed and caused some sort of havoc, (but left the cream.) 3) That there is a mountainous wall where something else might be going on.

In my opinion, I'd like to see some narrowing of focus within the first 13 of a short story. I'd like to hear more about the MC and her sick mother...perhaps the rest can be interwoven within you narrative later on?