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:
NOTE: If you have Dragonborn installed, then the Ring may be in Solstheim.
 * Ansilvund
 * Autumnwatch Tower
 * Bloodlet Throne
 * Bonestrewn Crest
 * Boulderfall Cave
 * Brinehammer
 * Broken Limb Camp
 * Broken Tower Redoubt
 * Clearpine Pond
 * Darkwater Pass
 * Dead Crone Rock
 * Dead Men's Respite
 * Driftshade Refuge
 * Druadach Redoubt
 * Eldersblood Peak
 * Fellglow Keep
 * Folgunthur
 * Forsaken Cave
 * Fort Fellhammer
 * Gallows Rock
 * Glenmoril Coven
 * Guldun Rock
 * Halldir's Cairn
 * Hela's Folly
 * Lost Tongue Overlook
 * Lost Valkygg
 * Moldering Ruins
 * Orotheim
 * Orphan Rock
 * Pride of Tel Vos
 * Rannveig's Fast
 * Rift Watchtower
 * Serpent's Bluff Redoubt
 * Shadowgreen Cavern
 * Shrouded Grove
 * Sightless Pit
 * Silverdrift Lair
 * Skyborn Altar
 * Sleeping Tree Camp
 * Southfringe Sanctum
 * Steepfall Burrow
 * Stony Creek Cave
 * The Katariah
 * Treva's Watch
 * Tumble Arch Pass
 * Uttering Hills Cave
 * Volskygge
 * Volunruud
 * Witchmist Grove

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 ring 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. A similar problem can occur if Dead Crone Rock is one of the ring locations.
 * Solution: Reload a save made before receiving the mission from Feran Sadri, and then initiate the quest again to be assigned different ring locations, ones that do work.
 * Possible solution for unobtainable rings:
 * Add the missing ring via console to the inventory (command "player.addItem ITEM_ID 1", where ITEM_ID is as follows: Ring of The Beast: 0200e7fd; Ring of the Erudite: 0200e7fe). Advance the quest stage via console. Try stages 10, 110, 120 (try the lower numbers first e.g. command "setstage DLC1RV08 110"). If all went well (and both rings are in possession), the Dragonborn should be able to report back to Castle Volkihar.