Eragon - Hidden Egg bonuses

1 Egg: Ad for the Eragon and Eldest books
2 Eggs: Edward John Speleers commentary
3 Eggs: Design commentary
4 Eggs: Art direction commentary
5 Eggs: Birth Of A Game commentary
6 Eggs: Concept art
7 Eggs: Orchestra commentary
8 Eggs: Saphira commentary
9 Eggs: Sienna Guillory commentary
10 Eggs: Character concept art
11 Eggs: Concept art
12 Eggs: Concept art
13 Eggs: Robert Carlyle commentary
14 Eggs: Sound Effects commentary
15 Eggs: Garrett Hedlund commentary
16 Eggs: Evolution Of Games commentary
17 Eggs: Concept art
18 Eggs: Throne Room bonus level

Defeating Durza:
When you reach Durza, continuously hold [Block] and use the fire move against him. However you will still have to dodge when he is about to grab you.

All eggs:
Go to the place where the things the other eggs had been unlocked and press Up, Down, Left, Right, Up, Up, Down and you should unlock all eggs.