Thanks to the moderator for placing this tale on the final day of the last fest. I spent my new year's eve with this, the story racing to the end as its clock counted up to midnight along with mine. (This may be the only story in the fest where I have an idea of the author's identity.)
What struck me most on first reading is that Regulus, Severus, Narcissa, and Lucius are each as obsessed with triumphing over death as Voldemort was. Yet unlike Riddle's fear of death, their motivations are to be with loved ones, their extended family of Slytherins, and in the end they are reunited in a similar way to the generation of Gryffindors who escort Harry to face Voldemort.
I like how it's all about Lucius' heart, the physiological damage to it leading to his final choice, and the fact that, yes, he has one in the symbolic sense.
I'll be re-reading to savor details like the arch's history, and the concept of essentia. Thank you, author.