Classic How do Death Knights grow in power?

Big part of my enjoyment of a class is the fantasy. Enough to make or break a class. I play Warlock mostly because the deliver of dark secrets and forbidden knowledge appeals to me. It makes sense that the more I know the more powerful I am.I want to understand Death Knight power progression. I understand they sustain themselves through inflicting suffering and death, that their power comes from a combination of their Runeblades and the magic the Lich King used to reanimate them, perhaps more.What is the equivalent of finding a new tome of lost knowledge for a Warlock to a Death Knight? Find a better weapon? Kill 10 people today where yesterday I killed 5? If a Death Knight possesses the same book could they garner anything from it? Any thoughts will be appreciated. via /r/wow https://ift.tt/2MdNPOI