Originally Posted by Vegankat
I've thought about the RAB thing a lot today. I think it could
possibly be Regulus, and that he hid the horcrux in 12 Grimmauld place, and perhaps Mundungus gets it and possibly sells it to someone... I'm speculating quite a bit, here, though.
oh listen to THIS theory of his....
Who do you think R.A.B. is? Who do you think went with him into the cave?
"To the Dark Lord
I know I will be dead long before you read this but I want you to know that it was I who discovered 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."
R.A.B. is absolutely, without a doubt Regulus Black & the one that went with him to the cave was in fact Kreacher:
-We know he was a Death Eater that turned against Voldemort
-DE's are the only people that call Voldemort the "Dark Lord"
-Kreacher could travel in the boat along with Regulus without being detected and so that he could feed him the green liquid
-The locket mentioned in "Order of the Phoenix"...
"also a heavy locket that none of them could open"
It comes in the chapter "The Noble and Most Ancient House of Black" while Harry et. al., after de-doxying the curtains, are cleaning out a cabinet in the drawing room. The locked in Grimmauld Place is in fact the real Horcrux. Now, maybe Kreacher's motive in trying to save everything he could lay hands on was not just sentimentality - he had been instructed by Regulus to guard certain items, probably without knowing what these items might be. With the locket they found at Grimmauld place, it becomes very important that Harry inherited Sirius's possessions where that fact was pretty much glossed over in HBP. Also the side story with Mundungus Fletcher stealing items from Grimmauld Place would be completely unnecessary besides to support the locket theory.
OH MY GOD! I knew I kind of half thought of that. the locket!!!!