After being swallowed in Avari's arcane weaponary to his demise, the so-called, Anathamancer met his end in the void world of Genot-Paine a place inside Avari. The evil sword Rendgray remains powerful and Avari learns that its disenchantment may be a long journey, not simply the turning of a proverbial key.
Avari's apartment in Niskantel is appropriately above the library. It is her belief from her studies that she has the potential to shut down the evil sword Rendgrey as an evil force in the world. It may be that the mystery of this is the mystery of herself.