Fire Emblem: The Sacred Stones/Chapter 6: Victims of War

Defeat the boss
It is recommended to get Torches for Natasha and Moulder, as it helps a lot with expanding the view. Also, Colm will mention that he has a wider view range, so you can use him if you like, but for expanding the view, Natasha and Moulder with Torches is much better. You can get Torches from the Shop at Serafew (Ch. 5)

If you have at least two units that can stay alive for a few turns without help, you should charge in and take the small fort in the middle of the map. Try to keep vulnerable characters in the back or else they WILL be swarmed by the enemies. Try not to sent a mounted unit up too far because there is a fighter with a Halberd that can make a huge dent in their HP if not kill them outright.

You'll need to sneak Vanessa by through the lower part of the map, getting the antitoxin from the village on the way. Here's where training her makes a difference. If you think she's strong enough, send her in to kill the Bael (spider). If you think it'll be too much for her, try to relocate the civilians to a lower location by turn 9 or the Bael will kill them one by one. If you manage to save all three by the time you finish the chapter, you'll get an Orion's Bolt for Neimi.

Boss: Novala
You can easily kill him with Seth but using someone that needs the experience is recommended. Artur can easily beat him since he has the weapon advantage but Novala doesn't really have good defense so he can fall easily to a good, strong character.