Specifically, the first paragraph is too long, and there are some fairly long run-on sentences which could be split into 3 sentances.
"As the boy grew older he was taught all sorts of things, from how to fight to how to have proper etiquette at a dinner table full of foreign dignitaries, until one afternoon, after a long day teaching the boy how to fight he was given the destined dagger, that day would mark the day that the kingdom of Daltum would fall."
Remove the "Until" and rework the second.
"One afternoon, after a gruelling training session , the young prince was presented with the Dagger (by who, specifically?). This afternoon would also be marked as the day."
Again, great background detail, but it is a bit - empty - of drama. The immense issue of oxygen depetion is touched upon, but otherwise this is almost too positive a sub for the general grimness of the Cosmic Era. Go to Comment
He is looking for a very high standard in this advice - "If your post could not be part of a published fantasy novel, it needs work" which is good for writing, though the main goal of this site is to share ideas. As a result, submissions should be made with an eye towards this goal, but this is certainly not the be-all and end all.
This makes a great backdrop to such things as Gamma world and Fallout - these changes could have been in progress when the shit hit the fan. As a result, your survivors can draw from the various castes listed.
I like this piece - always a sucker for the technical details.
One detail struck me as odd - you mention blackpowder as the propellent. Why not cordite? Blackpowder has a lot of disadvantages - not the least of which is the terrible fouling of complex machinery of which the mech would be one of.