Kindred Judgment

It serves as the final quest of the add-on.

Background
The quest begins with the acquisition of Auriel's Bow at the conculsion of Touching the Sky, after which Harkon must be confronted. The stages of the quest vary slightly depending upon what faction has been joined.

Dawnguard alignment
If the Dawnguard questline has been followed, instructions are received from Serana to return to Isran to formulate a plan of attack. After speaking to Isran, he will agree that now is the time to strike the Vampires and will call all the members of the Dawnguard into the main lobby for a rousing speech:

Isran: ''"For too long we've allowed these vampires to poison the night and kill our people! Now we finally have the means to strike back! We now have Auriel's Bow. The gods themselves have favored us and we must answer with action!

The time has come to finally put an end to Harkon and his unholy prophecy! We will march on their lair and destroy those wretched abominations so they can no longer corrupt our world.! This is our fight, and this is our fate. This is the time of the Dawnguard!"''

After the speech, Isran, Sorine Jurard, Celann, Agmaer, Gunmar, and an Armored Troll will leave the fort and begin their long trek towards Castle Volkihar to join in the final battle. Upon reaching the shores of the island they will wait for the Dragonborn before storming the castle.

Heading across the bridge will cause the Gargoyle statues that line the bridge to animate and attack. Several vampires will pour out of the castle, including Rargal Thrallmaster, Modhna, Namasur, and Garmr. This is one of the few opportunities where firing Sunhallowed Arrows into the sun with Auriel's Bow will provide additional help, provided it's daytime.

Once these foes are dead, Castle Volkihar can be entered. Inside, the remaining vampires will attack, including Hestla, Salonia Caelia, Fura Bloodmouth, Orthjolf, Vingalmo, Garan Marethi, Ronthil, and Feran Sadri. These vampires may be defeated or fought through to proceed into cathedral for the final confrontation.

Vampire alignment
If the Volkihar Vampires have been sided with, then after speaking with Serana head directly to Castle Volkihar. Several members of the court will be loitering around the castle as usual, each with some additional dialogue relating to the finding Auriel's bow. Follow the objective marker and enter the castle's cathedral.

Confrontation with Harkon
Upon entering the catherdral, Harkon will be waiting in his Vampire Lord form and willl initiate a conversation with Serana:

Harkon: "So, you've returned. Is your... pet keeping you entertained?" Serana: "You know why we're here." Harkon: "Of course I do. You disappoint me, Serana. You've taken everything I provided for you and thrown it all away for this... pathetic being/half-breed vampire." Serana: "Provided for me? Are you insane? You've destroyed our family. You've killed other vampires. All over some prophecy that we barely understand. No more. I'm done with you. You will not touch him/her." Harkon: "So, I see this dragon has fangs. Your voice drips with the venom of your mother's influence. How alike you've become. Serana: "No...Because unlike her, I'm not afraid of you. Not anymore." Harkon: "And you...

At this point he turns to the Dragonborn. The following conversation between Harkon and the Dragonborn will vary slightly depending upon what faction has been joined:

Dawnguard alignment
"It appears I have you to thank for turning my daughter against me. I knew it was only a matter of time before she'd return with hatred in her heart."

Hatred born of your neglect: "A small price to pay for the betterment of our kind."


 * Your kind is a blight on this world: "Yes, yes. Always the noble vampire hunter. And what happens when you've slain me? Is Valerica next? Is Serana?"

This in turn leads to three options to choose from:

'''I would never harm Serana. She's too important to me:' "Then my daughter is truly lost. She died the moment she accepted a mortal into her life."''

I'm only here to kill you: "I see. Interesting that you can set aside your morals when it suits you."

This is about more than killing vampires: "Ah, of course. The prophecy. You've come here to stop me from taking Auriel's Bow and shrouding the world in darkness."

Vampire alignment
"It appears I have you to thank for turning my daughter against me. I knew it was only a matter of time before your ambition outgrew your loyalty."

'''Loyalty? You never intended to let me live:' "A small price to pay for the betterment of our kind."''


 * You're an insult to our kind: "Oh, come now... spare me your notions of kinship. You've simply used Serana in an attempt to take away what should rightfully be mine."

This in turn leads to three options to choose from:

I would never use Serana like that: "The vampire is eternal, and with immortality comes the revelation that these bonds never endure... it's fleeting, momentary at best."

No, I'm here to prevent our annihilation: "Ah, I see you've been speaking to Valerica and she's convinced you that eternal night will plunge us into war with daytime dwellers. If only it were so. With the world in shadow, we would never tire, never weaken... more than a match for their pitiful armies."

The bow belongs to me now: "Finally, a trace of honesty in our little conversation. How does it feel to hold the fate of the vampire in your grasp. Exhilarating, isn't it? "

Finally, the last set of options is the same for both alignments and they end in having to choose between giving him the bow or refusing. Both options result in him becoming hostile.

Enough of this!: "Yes, quite. I'm growing weary of speaking to you and my traitorous daughter. I'll give you a single chance to turn over the bow to me. There will not be a second."
 * Never: "Very well then, you leave me no choice!"
 * Very well: (Give Auriel's Bow): "Pitiful. Simply pitiful. I expected more from the defiant fool that beguiled my daughter. No matter. Serana will sacrifice her blood for the sake of the prophecy, and I will feast upon yours in Molag Bal's honor!"

... "Little patience for talk? Good. Let's end this!"

Final battle
Lord Harkon uses the Bat's Night Power when damaged enough and begins attacking from above on the balcony. After his health is depleted, he will retreat to the blood fountain and be invincible while he heals, unless Auriel's Bow is used, which will cause his barrier to vanish. He will summon Gargoyles, which will necessitate close range combat. The process repeats itself until he dies with a unique death sequence of a very bloody explosion and his final words calling out to his daughter ''"No... Serana... your own father....". ''

If the bow was given to him, it can be looted off his body along with his Vampire Royal Armor and Harkon's Sword.

Epilogue
Once the battle is over either Isran or Garan Marethi, depending upon alignment, will walk into the catherdral and congratulate the Dragonborn for ending Harkon's plans.

Isran
Isran: "It's over. He's dead, and the the prophecy dies with him. I... I suppose this is difficult for you." Serana: "I think my father died a long time ago. This was just... the end of something else. I did what needed to be done. Nothing more." Isran: "I think perhaps... I think you did more than that. You have my thanks."''

''"So, the beast is destroyed. Not only that, but Auriel's Bow is in safe hands. The Dawnguard will now be dedicated to safeguarding it, making sure that the prophecy will never come to pass. You've served Skyrim well. Even with these vampires gone, the fight still isn't completely over. Once we're settled in back at the fort, there will be more work to do. We'd be honored to have you join us."

Garan Marethi
Garan Marethi: "Lord Harkon defeated. I never imagined I'd see the day. My congratulations on defeating Harkon. Clearly, you are the superior vampire. You are the new Master; we bow to your power. A power which, I note, includes Auriel's Bow. My lady, you have my deepest sympathies. I am sure this was not easy for you." Serana: "He was out of control Garan. It had to be done. I'm not happy about this. He... he was still my father. But I suppose my father really died a long time ago. This was just the end of something else." Garan Marethi: "Of course my dear. All will be well now."

If the Dragonborn is a member of the Volkihar Vampires, Castle Volkihar becomes a home, with every item therein belonging to the Dragonborn. The quest ends with Serana saying a few words about her father and asking if she can come along on future adventures.

Trivia

 * If the Dovakhiin is a Vampire Isran will refuse to speak with you until you've become cured.
 * To defeat Harkon very quickly, run towards the balcony behind him while he still converses with Serana. Crouch to sneak and fire an arrow at him with Auriel's Bow. With enough Fortify Archery and Archery skill, or an improved Auriel's bow, Harkon can be killed with one shot because of the sneaking damage multiplier.
 * Sneaking directly behind Harkon while he converses with Serana can also be a good way to finish Harkon with a single hit. You will however need to have sufficient skill with melee attacks and sneaking to deliver enough damage so that Harkon cannot warp away after being hit.
 * If played as a member of the Dawnguard, the Armored Troll may remain outside Castle Volkihar after the main quest has finished (if it was not killed). It will still be there if the player leaves and then returns.
 * After the completion of this quest, the two Elder Scrolls (Blood and Sun) can be sold to blind Moth Priest Dexion Evicus for 6000 gold. Alternately, they can be given to Dexion for free. Conversation with Dexion suggests a third alternative involving indestructible armor, but following that line accomplishes nothing. The two scrolls may also be kept, but they appear to serve no further purpose.

Bugs

 * Auriel's Bow can vanish from Harkon's remains.
 * Harkon may walk out of the cathedral, non-hostile, leaving the player behind.
 * Picking up the bow may not start the quest.
 * Halfway through the final battle with Harkon, he may freeze up and it may not be possible to kill him.
 * Serana may become stuck in a battle-ready position at the beginning of the quest, most likely due to the dialogue with the Falmer at the end of the prior quest. Serana can not be spoken with, making it impossible to complete the first step of the quest.
 * Solution: attack Serana until she loses all of her Health. Wait for her to recover, and speak to her again.
 * The objective to talk to Isran may still be up, even after talking to him, meaning any future speech will not start.
 * Harkon can collapse into ash but still heal himself, even though he has died. The game will act as if he is still there, and Isran and an Armored Troll will attack his location rather than mention how it is finished. Serana will also attack, meaning she will not wrap up the fight and DLC.
 * Gunmar can be pointed to at Castle Volkihar after the quest, but upon entering may not be there.
 * When aligned with the Dawnguard, it is possible to use Whirlwind Sprint to bypass the gate at Castle Volkihar, thus skipping strait to the confrontation Harkon without speaking to Isran.