For discussion of the sequel film to The Hobbit see:
The Bridge Film Hobbit Sequel
The Necromancer's domain
Dol Guldur, by Joe Russell
The Necromancer storyline provides a strong link between The Hobbit and Tolkien's darker trilogy The Lord of the Rings.
Halfway through The Hobbit story Gandalf departs Thorin and Bilbo’s company to pursue his ‘pressing business’ to the south. This business is the threat of the Necromancer, a dark sorcerer that dwells in the tower of Dol Guldur at the southern reaches of Mirkwood. At the start of The Hobbit Gandalf describes how he secretly entered the dreaded dungeons of the Necromancer nearly a century before and found Thorin’s father Thrain imprisoned there. Thrain had been tormented to madness, but Gandalf managed to recover his map of Erebor and key from him. A hundred years later at Bag End Gandalf gives these to Thorin and they prove vital in the quest for the Lonely Mountain. The next mention of the Necromancer comes at the end of The Hobbit story we learn that while Bilbo and the dwarves were tackling the dragon, the White Council drove the Necromancer out of Mirkwood.
When writing Lord of the Rings, Tolkien wove the Necromancer story into the much larger tale of the rise of Sauron (as described in the Appendices). The Necromancer became the early guise of the dark lord Sauron. Gandalf convinces the White Council (led by the treacherous Saruman) to attack Dol Guldur, only to find Sauron retreats to redouble his strength in Mordor.
The two film proposal put forward by The Hobbit filmmakers indicates that the Necromancer storyline will be expanded on. It would be possible to turn The Hobbit film into a dual narrative, as in Tolkien's Quest for Erebor. This approach would however clash with The Hobbit story, diminishing Bilbo as the central character and emphasising the inconsistencies between The Hobbit and Lord of the Rings regarding the action of the One Ring. Instead the filmmakers have proposed covering the White Council and Necromancer storylines in a second Hobbit Sequel film, the 'Bridge Film' linking between The Hobbit and Lord of the Rings.
To compliment the Bridge Film, the allusions to the Necromancer could be emphasised more in The Hobbit. In my proposal the Great Goblin and Elven King characters make more direct references to the Necromancer, and the history of Thrain's fate at the hands of the Necromancer is highlighted (though I believe the full telling of this story should wait for the sequel film). Another option would be to remove all references to the Bridge Film and avoid foreshadowing the sequel film plot. Certainly Gandalf's announcement at the end of The Hobbit that the Necromancer has been driven out of Mirkwood will have to be removed to avoid spoiling the climax to the Bridge Film (follow link for further Bridge Film discussion).
View my Hobbit Film Adaptation in pdf format.