Really nice! I like the careful set-up, the effective way you establish character before moving on to any smut. Everyone is nicely IC, and all the background details are fun (like Severus's skill with potions and spells; the idea that Sirius will be oblivious to the warning signs with Peter, etc.) You connect everything to Regulus's family story really well And your Remus is hot: there's enough of the wolf left in him to make him perfectly aggressive in the best of ways.