You don't need to indent your paragraphs unless you are writting a school paper.

Should the citizens of Canterlot has cause for concern?

That 'Has's should be 'have'.

Though the darkness was heavy, and unyielding, Shining could still make out the strange, alien vocalisations of the swarm that chased them.

You don't need the first comma there.

squad-mates, their bodies still, and unresponsive.

You don't need the comma between 'still' and 'unresponsive'.

4680509 yes you do

If you don't you break the unspoken rule