The Martinelli's Ring of Clear Thought is a vampiric artifact.
This gold ring was the property of a Malkavian elder destroyed during the Anarch Revolt. A ghoul created it for her as a gift. Wearing the ring removes all fears, phobias, Derangements and any mental flaws the individual wearing the ring might have. Removing the ring brings them back twice as strong, and the wearer becomes obsessed with recovering it.
Players Guide to the Sabbat, p. 153-154