One of the many factions that you can earn reputation in the World of Warcraft: Wrath of the Lich King, is the order called the Knights of the Ebon Blade.  This group is made up of Death Knights who have made their home at the Ebon Hold in the Eastern Plaguelands. They also have bases at the Ebon Watch in Zul'Drak and the Shadow Vault in Icecrown. The main area players will see them is around the Shadow Vault as they quest in there while attempting to gain reputation with them to earn rewards.

There are a vast number of quests that you can do to earn reputation with the Knights of the Ebon Blade.  Before you are level 80 you can start to earn reputation with the Knights by following the quest chain that starts with An Invitation, of Sorts.  The chain starts   with a drop off of a Withered Troll outside of the Ebon camp in Zul’drak. The quest line gives about 1,900 rep in addition to the other quests available at the outpost.

You can find all the details in our Knights of the Ebon Blade Reputation Guide.