If you go into the DLC area for the Earth raid (Possibly releasing with the House of Wolves DLC) you can see a gigantic AI through a large glass window. Perhaps this is Rasputin. I hope it is. HADAL could be referring to the fact that he has hidden himself in an underground bunker perhaps. If you haven't glitches into the Earth DLC I recommend watching videos or doing it yourself. A lot can be learned about lore through this.