Skyrim: Kindred Judgment
Kindred Judgment is the final quest in Skyrim: Dawnguard.
 Starting Location
The quest Kindred Judgment starts on the balcony outside the Inner Sanctum
 Quest Giver
With Auriel's Bow in my possession, it's time to confront Harkon and reshape the prophecy as I see it.
Confront Harkon with Auriel's Bow
Go to Castle Volkihar
Find Lord Harkon in the Chapel
Refuse to give him Auriel's Bow
(If you surrender the bow to him, he will betray you and attack anyway)
Fight Lord Harkon.
When Lord Harkon raises a blood shield, use Auriel's Bow with Sunhallowed Arrows to penetrate the shield.