To have May join your force, follow these directions. After your ship crashes, do what you're supposed to do. Travel east from your new town. You'll find a river. If there is a cave surrounded by water, you're on the right track. Go North a little and then east. When You find a town, go in. Follow the person that is scared of you and when you get to his house, talk to the old person. When he's done talking, go south of the village. You should see a centaur. Talk to her and she will join your force.