One thing that every artifact collector loathes about the Dawnguard addon is that both versions of the questline have mutually exclusive artifacts, meaning that you will always be locked out of acquiring some unique items no matter which path you choose. No longer. This mod adds an extra quest to each side of the questline which will lead you to the artifacts that would have been lost forever in the vanilla game.
The Dawnguard version begins after completing Kindred Judgement and the side quest Bolstering the Ranks; you'll receive a letter from Isran requesting that you track down a vampire who escaped the raid on Castle Volkihar with a number of vampire artifacts.
Artifacts unlocked by the Dawnguard epilogue:
-Ring of the Erudite
-Ring of the Beast
-Amulet of the Gargoyle
-Amulet of Bats
-Ancient Vampire Parts
-The Bloodstone Chalice
The Clan Volkihar version begins by reading a letter found on Isran during the side quest Destroying the Dawnguard.
Artifacts unlocked by the Clan Volkihar epilogue:
-Dawnguard Rune weapons
-Dwemer Crossbow Schematics and the ability to craft exploding bolts and enhanced crossbows.
-A number of undead-damaging spells that are exclusive to the Dawnguard merchants.
Contrary to what most people believe, this mod does, in fact, work with Legacy of the Dragonborn. Nothing from either will break if they are used together; you'll just end up with a few duplicates.