Oh, so much brilliance in so few words. I'm quite sure I won't be able to write a comment that does it justice, but I'll see what I can do...
You've done an absolutely astounding job of capturing the mind of Tom Riddle, right from the opening lines. I love the idea that deception and manipulation and guile come so natrually to him that he can't comprehend why others don't act in the same way. His jealousy of those who are in Grindelwald's favor and ultimately of Grindelwald himself is perfect. I can really sense the heat of his supporessed anger.
The parallels between the two scenes are so wonderfully conveyed. But, oh, Voldemort's arrogance! He selects Snape because he reminds him the most of himself at his first meeting with Grindelwald... but forgets that he was planning to ultimately overthrow and outshine Grindelwald even then! His arrogance truly is his downfall in the end.
I adored that you worked in the philosophy behind the name "Death Eaters." And this entire piece is filled with beautiful, haunting, descriptive writing. So, so well done.