When you reach Durza, keep holding BLOCK and use the fire move against him. However you will still have to dodge when he is about to grab you.

Collect the hidden eggs found throughout the game to unlock the following bonuses:

EGGS - BONUS
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

When the wave begins, useMagic Arrow to get a good start. When playing with another player, have Murtagh repeatedly fire arrows because of their speed. The Urgals that shoot fiery arrows are the most dangerous. The best way to defeat them is to fire a magic arrow, then go to them directly and kill them by grappling attacks. You can kill most of your enemies by using grappling attacks.