Skyrim Dawnguard Vampire Lord Walkthrough Part 16: Boneyard Keepers

Ask Valerica what you need to do. She tells you that you need to locate the tallest of the rocky spires that surround these ruins. At their bases, the barrier energy is being drawn from unfortunate souls that have been exiled here. Destroy the keepers that are tending them, and it should bring the barrier down. You tell her we will return soon. She gives you one last word of warning. There's a dragon that calls itself Durnehviir roaming the Cairn. Be wary of him. The Ideal masters have charged him with overseeing the keepers, and will undoubtedly intervene if you're perceived as a threat.

This completes the objective of speaking to Valerica, and you get your next task:

Beyond Death
Kill the Boneyard Keepers (0/3)

You can talk to Valerica some more to find out more about the Prophecy, and the Cairn. Your dialog options are:

Why haven't you pursued the Prophecy?
If I leave the Soul Cairn, can I safely return?
How did you become imprisoned here?

If you ask her why she had not pursued the prophecy, she tells you that Harkon's vision is a world plunged in eternal darkness where the vampire can flourish and never again fear the tyranny of the sun. What he fails to realize is how much attention would be called to out kind if the prophecy came to fruition. If eternal night fell, there are many who wouldn't stand for it. They would raise armies in attempts to return things to normal. The order of the day would be our destruction until every last vampire was hunted down and eliminated. Valerica prefers living in the shadows. It's how the vampire has survived for millennia, and the only way we can survive in the future.

When you ask Valerica about the possibility of leaving the Soul Cairn and returning, she tells you that as you have been traveling in the Soul Cairn, your body has become attuned to it. You should find no difficulty using the portal any longer.

If you are curious on how Valerica ended up being imprisoned in the Soul Cairn, she tells you that when she entered the Soul Cairn, she had intended to strike a bargain with the Ideal Masters, the custodians of this place. She wanted refuge in the Soul Cairn, and in exchange she would provide the ideal masters the souls that they craved. But they tricked her, unleashing the keepers to destroy her. Valerica was able to retreat into the ruins, but became trapped. The keepers, who were not able to claim her soul, instead constructed a barrier that Valerica couldn't breach.

You can also ask her who the Ideal Masters are. She knows little about them. They are mystic entities that lord over the Soul Cairn, controlling every aspect from its fabric to its appearance. Some necromancers believe that they resemble the crystalline structures dotting the Soul Cairn, but Valerica believes those crystals are just conduits. In return for the souls that necromancers feed the masters, the masters grant them the ability to summon powerful undead guardians as one would conjure an atronach or deadra. Though the majority of the necromancers end up as harvested souls themselves.

The direction of the Keepers should be marked on your compass. If not, make sure the quest is set as active. One of the Keepers is on top of a big ruined building, requiring climbing up two flights of stairs to get to him. Another one is in front of some sort of temple. Another one is inside the ruins of some castle. The keepers wear Dragonbone Armor and wield Dragonbone Weapons, so don't underestimate them.

The Keepers are quite a long distance from one another. If you have not already, it is recommended that you do the Arvak Flaming Mount quest so that you can travel through the Soul Cairn faster.

Once you have defeated all three keepers, Serana says that the Barrier should be gone now, and that you should return to where you found Valerica.