(See the full-version infographic of where these plot points came from)
Azog the Orc
The big bad from the first movie, for example, is only briefly mentioned in The Hobbit, but more devoted readers recognized this scene from Appendix A of The Lord of the Rings (the appendices are found at the end of The Return of the King, the third book in the trilogy): a battle between orc and dwarf raged at the east gate of Moria. The dwarf prince Thorin, grandson of the King Under the Mountain, received a mighty blow, cleaving his shield in two. Taking up a protective oak branch in its stead, Thorin began pummeling his foes, earning him the moniker Thorin Oakenshield.
Still, Jackson doesn’t get it exactly right. This business of Thorin amputating the arm of Azog, the albino orc king, for example, is poppycock so far as the books are concerned. According to Tolkien, Azog first brutally murders Thorin’s grandfather in a one-on-one encounter, and there’s no arm amputating or all-consuming vendetta following the dwarf-verus-orc showdown—which Azog does not survive. “I was calling Azog “Mobi-Orc,” like a cross between Moby Dick and Captain Ahab,” Drout said of his reaction while watching The Hobbit. “He’s got the missing limb and is after his enemy like Ahab is after the whale.”
Dol Guldur and the Darkness
One of The Hobbit’s more mysterious characters was the Necromancer, described only as a dark sorcerer of unknown origins.
Elrond describes “a time of watchful peace” after the first fall of Sauron and the taking of the One Ring, depicted in the battle with Isildur in the Fellowship of the Ring movie. But a darkness may be gathering at Dol Guldur, “the hill of sorcery” in Mirkwood forest where the Necromancer reportedly takes up shop. Radagast confirms these rumors by producing the Witch King's sword. These details (save the sword—that’s a Hollywood addition) mostly took place offstage in Tolkien’s The Hobbit, but Jackson weaves them into his version.
One other discrepancy exists, however: in Tolkien’s books, Mirkwood forest fell to darkness about 2,000 years before Bilbo’s journey, but for dramatic effect Jackson moved those events up to present day. Unlike the map depicted in The Hobbit (the book), Thorin’s version in the movie reads “Greenwood the Great” in place of “Mirkwood,” demonstrating Jackson’s attention to detail.
The White Council
In the Hobbit movie, Elrond and company form a White Council, where Gandalf urges his powerful colleagues to take action against the growing darkness in Mirkwood but wizard Saruman the White shoots him down (not yet turned evil as he is in the earlier film trilogy, but he’s starting to think about it). All of these details are covered in the Lord of the Rings and its appendices, though the Council’s discussions and decision to take action against the Necromancer occur over a period of 490 years in the series.