Identity of R.A.B
I have thought for quite a while about who R.A.B is, and I think I now know the answer. Read the note carefuly again:
To the Dark Lord
I now I will be dead long before you read this but I want you to know that it was I who dicovered your secret. I have stolen the real Horcrux and intend to destroy it as soon as I can.
I face death in the hope that when you meet your match you will be mortal once more.
Only Death Eaters address Voldermort as "the Dark Lord" remember? Remember when Harry questioned Snape during Occulumnecy lessons why does Snape calls Voldermort the Dark Lord cos only Death Eaters do that?
So he must be a Death Eater.
Which Death Eater has these initials?
Which Death Eater regretted joining Voldermort?
Which Death Eater knew he had to face death if he defected from Voldermort's side?
Copied from the Lexicon:
Regulus Black(1961? - 1980)
Younger brother of Sirius, favored by his parents as he shared their pureblood prejudices, to the point that he joined the Death Eaters. According to Sirius, "he [Regulus] got in so far, then panicked about what he was being asked to do, and tried to back out. Well, you don't just hand in your resignation to Voldemort. It's a lifetime of service or death" (OP6). Voldemort had Regulus killed sometime during 1980 (the same year the prophecy was made and Harry was born).
It fits doesn't it? A Death Eater, who knows he is going to die soon because he betrayed Voldermort.
I just need to know his middle name to confirm.