As requested - just proofreading for you. I'll go through the chapters and point out anything I notice. I know you probably won't want to correct anything yet as it would have to wait for validation but for when you don't have a new chapter waiting to go up:
(Words in capitals are those that I have added, substituted, or altered the spelling of. Most points relate to punctuation. I have tried to put my own comments in parentheses() to separate them from corrected quotes. (...) is my way of indicating the continuation of a sentence without writing it out in full)
"Of course," Selwyn replied
...everyone WHO was loyal.
"...their abilities, I..."
(It might also flow better if you were to alter the last sentence slightly as it is a new sentence)
"Selwyn sounded quite pleased with himself."
(would be one possibility - cutting the "said". Alternatively)
"Selwyn sounded quite pleased with himself as he said this"
(or something similar - it needs to be a sentence in its own right. The other option is)
"...our cause," Selwyn said, sounding...
"...for murder. HER MOTHER ended up starving herself..."
(not ideal but it would make it clearer who is being referred to - at first glance it appears to be the daughter.)
"...Bailey, Bailey Miller," interrupted the boy, who looked...
And CONSIDERING YOU'RE supposed to be...
(I believe that was what you were trying to say)
I will make it do more damage...
(This doesn't quite make sense. You might want to see if you can tighten it up a little) (3rd paragraph from bottom of page)
"... should trust these..." He paused, unable to find the right word. "People?"
(Or possibly a comma? I'm really not sure about these situations - I had one recently and in that instance resorted to a comma. It depends on the situation - in this instance I would tend towards the full stop.)
"...since Karkaroff. A man who..."
"Neither," growled Rabastan...
"...death." He threw Lucius across the room and as THE MAN crashed into...
(I really hate dealing with this kind of situation - two characters of the same gender, and you haave to make it clear who is currently "him" - best to be on the safe side and make it obvious - it helps the reader)
There was a WAIL of pain...
"...out of the way," Selwyn said casually, "I would like..."
(The next sentence is very long, and would probably look better split. One possibility:)
...back to Lucius. At last, lowering his wand, he turned his attention back to Selwyn and snatched the large rolled-up piece of parchment that Selwyn handed to him. He unrolled it and examined it carefully.
...from the parchment.
"These names, are they-"
"Most of them," Selwyn answered, "but we..."
"...next week. Do you really believe..."
"On the contrary," Selwyn said...their faces, "This is just..."
A lot of this is a bit picky, but as I'm commenting at all I thought I might as well pick out everything I could find. Main themes: punctuate at ends of speech, if just with a comma. Also make sure it's really clear who you're talking through so the reader doesn't have to go pause and figure it out. But as I said before, the main thing is to start a new line for each new speaker as this makes it so much easier to pick up on who is speaking at a time. If you pick anything out in my stories, please let me know (it's easier on someone else's)
OK, this is really long! I hope you find it useful - actually, weirdly enough, I find this thing kind of fun! And I hope I've made it clear what I mean. Now, on to chapter 2!