I was so keen on getting into wotlk again that I had boosted a char to 80. Since I want to get exalted with most of the factions to increase my gs I went to do the ebon blade quest chain to liberate the shadow vault. I found the dk of your faction npc (thalassian or koltira) and this npc did not have a quest for me to begin the chain.
You can unlock Ebon blade in 2 ways
1. [Preparations for War] which requires level 77, Cold Weather and parts of the Wrathgate chain
2. [Crusader's Pinnacle] which requires Argent Vanguard