The Battle of Farthen Dûr is a nasty, back and forth slugfest whose conclusion ties up some loose ends for us. Throughout Eragon, we see the long arm of the evil King Galbatorix try to reach out and snatch Eragon and Saphira up in his claws. While the novel begins with them chasing the Ra'zac to avenge Eragon's dead Uncle Garrow, at some point the roles reverse and the hunters become the hunted.
After they're chased all the way to the Varden's hideout in the mountain of Farthen Dûr, though, the chase comes to an end. No more cat and mouse games. After the Urgals make their way into the tunnels under the Varden's city of Tronjheim, their backs are against the wall. It is time to get it on.
The Varden prepare defenses, and then wait for the Urgals to show their ugly mugs. When they finally do, we really wish this guy were on hand before the fighting starts to go down. In any case, the battle eventually goes the way of the good guys, after Eragon manages to slay Durza the Shade. Party time, right?
Well, not exactly. The battle has cost the Varden dearly, and they lose their leader Ajihad in a sneak attack. For his part, Eragon is pretty badly scratched up by Durza. As he lies in recovery, he reflects upon his newfound status as a legit Dragon Rider. It seems that the battle has given him the confidence to at long last accept his destiny.
Oh, and don't forget: Eragon is also visited in his mind by the Cripple Who is Whole. This voice promises Eragon answers and protection, and the last thing we see is his resolution to go with Saphira and seek this person out. Can someone say sequel?