Farkas spent the night with Verianus and saw her off in the morning, Lydia at his side. Before she bid them a final farewell, Farkas leaned in and whispered something in Verianus' ear. She smiled and kissed him once more before he sent her off on her journey back to Fort Dawnguard, knowing she would return to them- to him.
Once she returned to the fort, Isran shined sunlight on them to make certain that she, Gunmar, and Sorine weren't vampires. He filled them in on what had happened, then asked Verianus to come with him to find out why a vampire came to the fort asking for her by name.
Serana, the vampire woman that Verianus had escorted to her family's castle, had come seeking Verianus' help. She explained that her father was a fanatic and obsessed with a prophecy told in the Elder Scroll she carried. She wanted to find out why and knew that they needed to stop her father before it was too late.
Verianus and Serana were tasked with seeking out a Moth Priest who had come to Skyrim in search of the Elder Scrolls. They were able to track him down to Dragonbridge, but his caravan had already left. They hurried to catch it, but when they found the wagon it was capsized on the side of the road with the Imperials from the caravan and one of the vampires that had attacked the caravan dead. They found a note on the vampire, then hurried to rescue the Moth Priest. Taking out the vampires and their death hounds was no trouble, but they had to free the Moth Priest from his prison and dispel the vampires' hold over him. Once they had accomplished that, they escorted him back to the fort where he prepared for reading from the Elder Scroll. Upon reading from Serana's Elder Scroll, they learned of part of the prophecy that Harkon was obsessed with and of Auriel's Bow. To complete the prophecy, they needed two other Elder Scrolls- the Dragon and the Blood. Verianus still had the Dragon scroll, but they needed to find Serana's mother, Valerica, in order to retrieve the Blood scroll.
Serana and Verianus figured that Valerica had to be hiding somewhere in Castle Volkihar, in a place that Harkon would not look for her. Serana suggested her mother's old garden, mentioning that her father hated going there. Agreeing that was the best place to start, they made their way back to the castle- using the secret entrance Serana mentioned to slip into the castle unseen. They made their way through the undercroft and into the courtyard, finding Valerica's garden in disarray. While Serana tried to figure out what was wrong with the sundial at the center of the garden, Verianus noticed a few of the crests were missing and spotted them scattered throughout the garden. She gathered them up and placed them in their respective places, opening a hidden passage beneath the dial that not even Serana knew of.
They traveled down the stairs and into the ruins beneath the castle, finding their way through skeletons and gargoyles until they reached Valerica's study. Serana and Verianus went about searching the study for any sign as to where Valerica could have gone, finding her journal. Serana read through it, reading off the list of ingredients written down as Verianus gathered them up. When they had gathered all but one ingredient, they stood at the designated basin. Serana explained that her mother had found a way to open a portal to the Soul Cairn, a place where necromancers could draw souls from and store into soul gems, but they needed her mother's blood to open the portal. Veranius pointed out that she had her mother's blood and Serana agreed to try it. She combined the ingredients- her blood included- in the basin and the portal opened, glowing with an array of purples.
Veranius tried to make her way through the portal, but something lashed out at her. Serana explained that it was most likely because she didn't meet the conditions to pass through the portal unharmed, leaving them with two options: Veranius could allow her to turn her into a vampire, or she could allow her to trap a part of her soul in a soul gem and offer it as payment- the latter of which they could retrieve from the Soul Cairn before they leave it and restore that part of her soul. Verianus thought over the options, knowing that trapping her soul- even a part of it- in a soul gem could be incredibly dangerous. Becoming a vampire would mean she lost the beast blood she shared with the Circle and it could greatly affect her relationship with Farkas. Choosing to allow Serana to turn her, Verianus bore the pain of the transformation and they quickly passed through the portal and into the Soul Cairn to search for her mother.
The search didn't take long, Verianus feeling drawn towards the location of the Elder Scroll when the familiar energy sang to her. Upon finding Valerica, however, they discovered that she was trapped behind a barrier put in place by the Ideal Masters- the "guardians" of the Soul Cairn. After a "heartfelt" reunion, Valerica and Serana discussed the situation and Valerica chose to begrudgingly place her trust in Verianus, tasking them with defeating the Keepers who maintained the barrier.
The Boneyard Keepers were no easy opponent, each of them towering over Serana and Verianus. They were able to work together, though, and overcome the Keepers- defeating each of them before returning to where Valerica waited. Valerica led the way into the Boneyard, warning to watch for the dragon Durnevhiir that resided within the Soul Cairn. Durnehviir, however, caught up with them and ambushed them in the Boneyard. With Serana and her mother's help, Verianus was able to take down the dragon- not surprised that she could not absorb his soul. Valerica warned that Durnehviir would respawn once he regained his strength and told Verianus and Serana to retrieve the scroll and hurry back to Tamriel. They quickly retrieved the scroll and made their way out of the Boneyard, finding Durnehviir waiting. Instead of attacking, though, Durnehviir commended Verianus on her victory over him and more importantly over Alduin. He explained how he came to be in the Soul Cairn, and that while he was trapped within it he wished to see his home once again. He taught Verianus his Thu'um and asked that she summon him in Tamriel in times of need. Agreeing to the dragon's request, Verianus and Serana hurried back to Tamriel and made their way back to Fort Dawnguard.