Fire Emblem: The Sacred Stones/Chapter 12: Landing at Taizel

Send a group left and a smaller group right when you arrive. Go up into the house and get Ewan, and use your smaller group to purge the other ship of enemies, then go group with the rest of your group. Kill the boss, do NOT kill Marissa, you don't need to get Ewan to talk to her to join your team, if you beat the boss she automatically joins at the end of the battle. If a few of your units are a bit underleveled, or you are short on cash, go fight in the arena before you kill the boss. It's your last chance to use one.