Beautiful and fraught with menace, the story and the characters both. I love the allure of your Gellert, how teasing and flirtatious he is even as he speaks of possibilities that are so dangerous. His fascinated discovery of Albus, his delight in his own greater experience despite his status as the younger, and the way he plays Albus's own body and even his accoutrements against him -- all made this very compelling.
I also really liked the way you wove exposition through this story, how Albus's daily duty of clearing his mother's grave provided an opportunity to unfold the point in the timeline and the pervading sense of Albus's entrapment. The brief mentions of the dynamics with both Ariana and Aberforth worked extremely well, providing readers with the complexity of their difficult family situation and the various family members' reactions to that situation.
Such a wonderful, haunting fic. I'd tell you my favorite turns of phrase, but I've already rattled on too long; suffice to say that your prose is rich and vivid while at the same time always ensuring the main focus is on the narrative and character interactions. Extremely well done.