Fire Emblem: The Sacred Stones/Chapter 7: Waterside Renvall

Send Neimi, and anyone else you want (I chose Florina, as she can bring neimi back over the river to the main group when the ballista breaks, or has no-one else to hit in range.) north to kill the pirate and mage and use the ballista. Send the rest of the group east, winding throughout the path. If you brought seth, use him to take out the ballista and other person in the north east.

Use someone with a lance to kill Murray, and any ranged characters you brought could help if they can hit and do damage to him.