The thing about the āVoldemort gave Abraxas the diary and not Luciusā theory that just irks me is that we actually have no proof in the books that he was a member of the original Death Eater core despite attending Hogwarts around the same time as Tom.
āGood gracious, is it that time already?ā said Slughorn. āYouād better get going, boys, or weāll all be in trouble. Lestrange, I want your essay by tomorrow or itās detention. Same goes for you, Avery.ā - Half-Blood Prince, Chapter 17
āThen if I were to go to the Hogās Head tonight, I would not find a group of them ā Nott, Rosier, Muldber, Dolohov ā awaiting your return? Devoted friends indeed, to travel this far with you on a snowy night, merely to wish you luck as you attempted to secure a teaching post.ā - Half-Blood Prince, Chapter 20
Meanwhile, Iād also argue that thereās far more proof that he wasnāt a Death Eater or even Death Eater-adjacent given that Draco brings him up to Slughorn after learning that the man is cutting his favour from students heād otherwise give it to if not for the fact that their fathers are proven Death Eaters.
āWell, I pity Slughornās taste. Maybe heās going a bit senile. Shame, my father always said he was a good wizard in his day. My father used to be a bit of a favorite of his. Slughorn probably hasnāt heard Iām on the train, orāā
āI wouldnāt bank on an invitation,ā said Zabini. āHe asked me about Nottās father when I first arrived. They used to be old friends, apparently, but when he heard heād been caught at the Ministry he didnāt look happy, and Nott didnāt get an invitation, did he? I donāt think Slughornās interested in Death Eaters.ā - Half-Blood Prince, Chapter 7
āSir, I think you knew my grandfather, Abraxas Malfoy?ā Harry looked up; Slughorn was just passing the Slytherin table. - Half-blood Prince, Chapter 9
As a result, I think that thereās more than enough context to believe that the Malfoy that Voldemort is referring to in DH when addressing the Horcruxes is actually Luciusā¦
And Hogwarts... but he knew the his Horcrux there was safe; it would be impossible for Potter to enter Hogsmeade without detection, let alone the school. Nevertheless, it would be prudent to alert Snape to the fact that the boy might try to reenter the castle. ... To tell Snape why the boy might return would be foolish, of course; it had been a grave mistake to trust Bellatrix and Malfoy. Didn't their stupidity and carelessness prove how unwise it was ever to trust? - Deathly Hallows, Chapter 27
ā¦to back up the claims that Dumbledore makes in the book prior about how Voldemort gave Lucius the diary.
āYes, he did, years ago, when he was sure he would be able to create more Horcruxes, but still Lucius was supposed to wait for Voldemorts say-so, and he never received it, for Voldemort vanished shortly after giving him the diary. No doubt he thought that Lucius would not dare do anything with the Horcrux other than guard it carefully, but he was counting too much upon Luciusās fear of a master who had been gone for years and whom Lucius believed dead. - Half-Blood Prince, Chapter 23
Iām generally more inclined to believe Dumbledore in regard to these later scenes than I am to his guesses about Merope and Young!Tom simply because the man had a reliable source in the room feeding him information about Voldemort and Lucius (aka, Snape). And while we can certainly be running up against the possibility that Dumbledore himself is lying to Harry, I donāt see any value in him trying to trick Harry into believing that Lucius was given the diary instead of Abraxas. And while I definitely donāt believe that Abraxas was some muggleborn-loving anti-purist rebel (he absolutely killed Nobby Leach), I think that itās far more likely that he and Tom were two leaders of a pair of rival blood supremacist movements that were vying for power during a time of great political upheaval in the aftermath of Grindelwaldās and not actual allies, and that Tomās much more extremist movement just picked up more traction in the aftermath of Leachās assassination.
[ Not to mention that Tom is just weird about fathers in general because of his own daddy issues, so it actually makes a lot more sense to me that Lucius became one of his First War favourites to rival the levels of Bellatrix and Rodolphus because he rebelled against his own father to join his cause instead. ]
