I liked the mood of this. It has that good lost-history feeling where the setting does not feel merely old, but wounded by what it remembers.
Structurally, I think the piece is strongest when it lets image and implication carry the weight. The commandment, the ruined relics, the hidden chamber, and the repeated marks all create a clear sense of forbidden inheritance. That gives the story a stronger pull than direct explanation would.
My small criticism is that the prose sometimes asks the reader to process a lot at once; title, faction terms, treasures, relationships, old grief, and immediate action.