This one isn't very difficult, but it's long and annoying. You have to defeat literally 400 troops, but along the way Saphira kills about 100 of them for you. Otherwise a very linear level, just keep killing enemies and following the path you're led on. In the final square, avoid the Krull and run in circles using magic arrows until your Saphira call comes up, you will need three of these and she will burn the remaining enemies to death.