Grindelwald - horcrux?
Ive just re read the whole series, and well a thought occured to me, Dumbledore knew about horcruxes. It says in HBP that horcrux has never been used in the plural term before, which makes me think that Grindelwald used a horcrux, it says he was a powerful Dark wizard. It makes sense, it shows how Dumbledore knows what they are and how to destroy them!What do you think?
Oh and also does it actually say Regulus is dead?!