The overall goal for the characters isn't going to be immediately clear, as a new Flight they'll potentially be struggling to find their place in the world, as well as answers to various questions such as what was the Silver Flight for and why was it apparently canceled? All will be revealed don't worry! The idea for what the characters are supposed to do is a little hard to answer, because I came into this with the concept of letting the characters do what they wanted and exploring the results. So take it for now, until individual goals pop up, that the main objective is to save what they can and defeat the Legion. By no means will this be short, or easy. All too many times Azeroth escapes destruction by the skin of its teeth, with future knowledge and infiltration skills you can make a difference, but in the beginning it will mostly be convincing others into action, and their personal power will have to be acquired and grown in their own.