The source of much rumor and speculation both within the game world and among fans, the Book of Medivh refers to a spellbook (or possibly two or more spellbooks) written by Medivh, the Last Guardian.
History
Although the Book of Medivh has not been seen in World of Warcraft, there have been references to The Book of Medivh in both Warcraft II: Beyond the Dark Portal and Warcraft III.
Warcraft II: Beyond the Dark Portal
Medivh's spellbook was kept in the Royal Library of New Stormwind following his death. Ner'zhul stole this book during the battles that took place following the Second War and used it to open many portals on Draenor. Ner'zhul also obtained the Jeweled Scepter of Sargeras and the Skull of Gul'dan, and the Eye of Dalaran. His portals ripped Draenor apart. Khadgar later stole the Book and the Skull back and used it to seal the Dark Portal. The game ends with the book in Khadgar's possession, trapped on the other side of the Dark Portal.
Warcraft III
Archmage Antonidas of the Kirin Tor apparently came into the posession of an artifact known as the Book of Medivh sometime before the Third War. It was stolen from Dalaran by Arthas and Kel'Thuzad during that war and used to summon Archimonde, thus beginning the Reign of Chaos. The book was last seen in Kel'Thuzad's possession. Kel'Thuzad referred to it as "the last surviving spellbook of Medivh, the Last Guardian."
One Book or Two?
There is some debate among the fan community as to whether the references to the Book of Medivh in Warcraft II: Beyond the Dark Portal and Warcraft III refer to the same book, or to different books. If they are the same, there is not yet an explanation for how the book returned to Azeroth from Draenor following the events of the war beyond the Dark Portal. Archimonde referred to the copy held in Dalaran as "the only remaining spellbook of Medivh, the Last Guardian." This would seem to imply there had been others at one time, and he may have presumed that the book in Khadgar's posession had been lost in the destruction of Draenor. It's also possible that Khagar's book was entitled The Book of Medivh, whereas the one acquired by Kel'Thuzad was simply a working spellbook.
Other
There are several places in upcoming patches or the expansion pack where the Book of Medivh might show up:
- The Necropolis Naxxramas -- Kel'Thuzad, the last known owner of the Book of Medivh, may "gain" it in his loot table when the expansion is released.
- Medivh's magical keep of Karazhan will be released as an instance in the expansion pack, and it is possible heretofore-unknown copies of his spellbooks remain there.
- Khadgar and his crew survived the destruction of Draenor and are still alive in Shattrah City, suggesting the original Book of Medivh may also have survived. It is possible his copy of the Book of Medivh may again come into play, or at least that some of the mysteries surrounding it will be clarified.
Medivh's Journal
In Karazhan the Shade of Nielas Aran, the involuntary father of Medivh, has a book of medivh. Mages from the Kirin Tor were looking for the book and went mad when they have read it. Kamsis gave it to Aran.
When you read the book at the Master's Terrace you can watch how Medivh killed the mighty blue dragon Arcanagos, now better known as Nightbane.