Important Part: Character is to be in possession of a very special spell book that actually belongs to a Vampiric Demon named Vesta, and holds a segment of her magical power within it. The book can only be opened by sacrificing a small portion of the user's blood to its pages and is full of very old Blood Magic spells/rituals, with a sprinkling of other related Dark/Black magic. The spells within would normally be considered evil/bad by most existing magical disciplines. Within the inside cover of the ancient book is a handwritten note detailing a list of six items underneath the header "To Release Me": Ritual Dagger; Jewelry Key; Signet Ring; Seeing Glass; Talisman; Mistress of Death. *Note: Vesta WILL be out to retake possession of this item ICly
Other Background: The item is associated with a Site-Lore Legend of a Vampiric woman, nicknamed the "Mistress of Death", who was forced to 6/7ths of her magical power as part of the ratification of the Onyx Treaty when all that is Divine, Arcane, Supernatural, and Magical became hidden from humankind. Some versions of the legend claim she was trying to become a Goddess (A popular claim of the Fae), some say the powers that be were jealous of her worldly influence, some claim that a single person would be able to steal and/or control her power if they were to reunite all the artifacts, etc etc there's a whole bunch of options for fun stories and potential misunderstandings.
Initial Idea: I wouldn't mind having some sort of Frenemy foundation where there's a character that is actually out to try and find this ancient demon and somehow bind her to his or her will/goals. While of course at the same time she plays along trying to use the would-be conqueror's resources to help her find her own artifacts. Example Trope: Dueling Chessmasters. Bonus points if spellbook owner actually is evil-ish and wants to break the Treaty entirely, or return the Old Magic to the world, any number of "frowned upon" goalsets. Open to the initial relationship evolving in other directions based upon what happens in threads.
Axillary Idea: Could also be somebody Hellbent on keeping her "evil" powers bound and the Onyx Treaty unbroken, or believe her a harbinger of the apocalypse, etc.
Character Details: Individual details all up to the player - Human, Elf, Faerie, Liche, whatever creature you want. Doesn't have to be a sorcerer even, I just put that because it would be the easiest "class" of character to find practical use for the book. (Although, to be honest, the idea of some sort of Dragon creature that likes to horde ancient magical items wanting to make her stuff part of his/her 'Collection' sounds hilarious too)