Rings of Blood Magic

It's only available if the Dragonborn chose to become a Vampire Lord at the end of Bloodline.

Background
The quest is initiated by talking to Volkihar Castle's resident alchemist, Feran Sadri. He will tell the Dragonborn that two powerful rings given to ancient Vampire lords by Molag Bal have found their way to less favourable owners. Feran wants the Dragonborn to retrieve the rings to have them back in a Vampire Lord's hands.

The Ring of the Beast and the Ring of the Erudite are powerful rings that augment the Vampire Lord's special abilities while transformed and increases their attributes while in humanoid form.

Objectives

 * Find the Ring of the Beast.
 * Find the Ring of the Erudite.
 * Return to Feran Sadri.

Walkthrough
Go to the radiant locations marked in the journal, the ring will either be on a leveled boss enemy, or in a chest.

Possible locations

 * Bloodlet Throne
 * Broken Tower Redoubt
 * Dead Crone Rock
 * Dead Men's Respite
 * Glenmoril Coven
 * Halldir's Cairn
 * Lost Valkygg
 * Orotheim
 * Orphan Rock
 * Pride of Tel Vos
 * Rannveig's Fast
 * Sightless Pit
 * Skyborn Altar
 * The Katariah
 * Uttering Hills Cave
 * Lost Tongue Overlook
 * Southfringe Sanctum

Bugs

 * If a previously slain dragon priest is chosen as a bearer of one of the rings it may be impossible to complete as the body will have disappeared meaning the ring cannot be obtained.
 * You may find the Night Power Amulets at the same location as the rings.
 * If a previously slain Gauldurson from the quest "Forbidden Legend" is chosen as the bearer, the amulet may be unobtainable because they don't respawn. (Geirmund's Hall, Saarthal, Folgunthur)
 * If Uttering Hills Cave is chosen as the location of one of the rings, the player may find a quest marker hovering in Linwe's room but no ring, making the quest impossible to complete.