Cataclysm: The age of integration
Death knights, to put it lightly, didn't have a huge part in Cataclysm itself. For the most part, we may be able to assume that most death knights stayed in Northrend to help with containment and cleanup of the last of the Scourge, but of course, we don't see any of that. We have been told that the Ebon Blade, along with the Argent Crusade, is keeping an eye on Sylvanas, but unfortunately, they don't take much direct action as a group.
Luckily, we're not left bereft of any death knight development. Two of the more prominent death knights, Thassarian and Koltira, are now generals in their respective factions' armies and have come to clash at Andorhal. This, at least, implies a certain few things about the status of death knights in Horde and Alliance society.
It is certainly true that death knights were noted as barely trusted in the Wrath era, but in Cataclysm, we see two death knights as generals at the heads of rather important armies at Andorhal in Western Plaguelands, and there's no sign of dissension or distrust in their ranks. While there's always the chance of small pockets of people who still hate the death knights for their ties to the Scourge, the death knights' actions in Northrend seem to have essentially earned us some amount of respect and trust among our faction.
Lich Queen Rising: Death knights vs. Sylvanas
Of course, possibly the biggest story hook for death knights comes at the end of the Andorhal quest line. Thassarian and Koltira, acting in remembrance of their brotherhood as members of the Knights of the Ebon Blade, have been trading truces and peace agreements to allow each other to rest up, fight fresh, and fight fair.
Sylvanas, as one might expect, is having none of that, and captures Koltira in some kind of controlling spell, prompting Thassarian to vow to rescue him. This, of course, brings up quite a few questions. Will Thassarian be joined by others of the Ebon Blade? Will there a split between the Horde and Alliance death knights, in which the question of whether death knights are ultimately more loyal to the Ebon Blade or their own factions is called into question?
This question may be magnified by recently rumblings in lore. The Sylvanas short story painted the Dark Lady in a somewhat unflattering light, making her arrogant and vain in life and death alike, using her Forsaken allies as shields between herself and death, tools rather than beloved subjects. Then, of course, there is her willing and eager use of the plague in places such as Gilneas and Southshore. Just about everyone is starting to find reasons to take her out.
At the same time, we've been told that the Alliance is getting some love in Pandaria. The idea of taking out an opposing faction leader may seem a bit high, but hey, we took out both Fandral and Benedictus in Cataclysm, so taking down Sylvanas might not be as far-fetched if you think. If it does go down that way, The Knights of the Ebon Blade would be in a prime situation to take part, being experienced with the type of Lich King shenanigans going on, and with the extra incentive of rescuing Koltira. It would also prove that death knights, even after the death of Arthas, do have something to contribute to the world.
Of course, that's all back on the old world, and it's certainly still possible that Blizzard won't allow us to kill a character as popular as Sylvanas or that the Ebon Blade won't be directly involved. Luckily, there are still a few very interesting hooks Blizzard could use on Pandaria itself.
Sha, suffering, and the death knight
If there's a central villain to the lore of Pandaria so far, it's probably the Sha, a type of malevolent force that feeds off of negative energy. Think about that in relation to death knights for just a moment. Remember, lore-wise, death knights are required to cause pain and suffering in order to stay alive and sane. In other words, what feeds the Sha also feeds the death knights.
So what happens when death knights come to Pandaria en masse to help their factions? Will we have to face up to our very nature? Will our presence bolster the Sha even further? Or will our connection to the Sha's source of power allow us an understanding of their nature to such a way that we can harm or harness them in a way no one else can? It's a story hook I think has a lot of potential. It allows the Knights of the Ebon Blade to get a nice storyline update, and it allows a look into the Sha storyline that lends some complexity to the issue and elevates the storyline beyond "negative emotions bad."
The Lich King stirs
One other possibility I feel deserves a mention, even if it's less likely to come up than the other two possible story lines. Bolvar's had a full expansion to get his act together and really start discovering his power. While he's specifically setting himself up as a jailer of the dead rather than the conquering hero, Blizzard's had a theme of power corrupting for quite some time. Like Tal Rasha before him, will Bolvar succumb? Or will he feel some sort of compulsion to reach out and rein in the autonomous Scourge still operating in the Plaguelands -- or even the Valkyr who escaped his jails to serve Sylvanas?
If he does this kind of thing, one of the few organizations he might be able to reach out to with relatively safety is the death knights. As fellow former slaves of Arthas who also carry the burden of his necromantic taint in the back of their mind (the drive to kill in the back of their mind might be considered a lesser version of the Lich King's drive to conquer), it could be incredibly interesting to see the death knights return to their status as knights of the Lich King. They would, however, not function as heralds of destruction, but as fellow jailers, wardens of the dead, using the Lich King's power once again to deal with threats no one else can handle.
It would certainly be a new direction. Sylvanas, Kerrigan, Tal Rasha, Arthas -- Blizzard seems to have a pattern of allowing heroes to fall to corruption, succumbing to their darker natures when tainted by an outside force, even if they started with good intentions or even became corrupted against their will. But so far, death knights have resisted that, as has Bolvar. Perhaps, in joining together, we'll continue to buck that trend, being a force for good, fighting external demons as well as internal ones.
Learn the ropes of endgame play with WoW Insider's DK 101 guide. Make yourself invaluable to your raid group with Mind Freeze and other interrupts, gear up with pre-heroic DPS gear or pre-heroic tank gear, and plot your path to tier 11/valor point DPS gear.