@Sir Jerric
I like the bodyguard Idea. Perhaps the two ordinary people are important and She was employed to protect them. But then She discovers a terrible conspiracy against them (perhaps to kill them?) that would destroy their world as they know it. Yet She, knowing that she cannot protect them tasks them with finding a mythical, nonexistent object that would put the two people out of harms way and thus helping her in a way she cannot do herself. Then She goes to try and stop the conspiracy and is captured somehow while trying to find out who is brewing the conspiracy (the mysterious antagonist). The two people find out that they were sent on a false quest and return in anger, only to find their home in ruins and their family dead, Then the two people rescue Her (who was captured) and stop the conspiracy (for now... ). This teaches Her that the two people were more than She thought they were and teaches her that ordinary people are capable of extraordinary things.
Here is the plotline (do whatever you want with it)
1. She is employed to protect 2 ordinary but important people
2. She then uncovers an conspiracy against them
3. She then sends them on a false quest. (I recommend you do not tell the readers that it is a false quest)
4. The two people go off on their adventure
5. She tries to find out who is behind the conspiracy
6. The two people find out that is a fool's quest (PLOT TWIST)
7. She is captured
8. The two people's home is destroyed and they are presumed dead(?)
9. The tow people return and find their family dead
10. The two people find out that She has been captured
11. The two people go and rescue her.
12. The antagonist is revealed unexpectedly
13. The group now go and stop the conspiracy
14. Their homeland acknowledges them as heroes
15. Status Quo Updated.
Whew.
Hmmmmm. This should turn out well. So the emperor may be a corrupt rich person with no care for his people. Major Villain is just a man with a vision and intends to claim the lands and govern the people. But even then they would be no better off as Major Villain is still a very, very bad person and intends to take control for himself not for the people. The emperor's daughter has been kidnapped for ransom but this is all a front. Minor Villain knows this and goes ahead as he realises that it will be beneficial to him (perhaps he is bribed to do so). You mentioned that they (royals) have magical powers, so lets say the powers can be harvested and the emperor's brother leads the army. Major Villain is a very powerful man and intends to bait the imperial army and the emperor's brother into an ambush and slaughters them after accepting the ransom. As the Emperor's brother has magical powers and is killed by Major Villain, lets say the emperor's brother's powers are transferred to his killer. In this case Major Villain. Then Minor Villain is allowed to go and kill the emperor's daughter and so also gain magical abilities. But the emperor's daughter escapes into the mountains where she is taken in by a group of magical people who teach her how to use her powers. After a few weeks she returns more powerful than ever and finds out that the emperor is dead. She then rallies all of her people ( remember Major Villain's rule is just as bad as the Emperor's if not worse) and takes back the kingdom. If you are planning a sequel, lets say at the end of the story Major Villain fakes his death and escapes.
As for what Major Villain is offering Minor Villain, I guess it should now be obvious, Minor Villain is offered wealth, nobility, magical abilities and other stuff. Lets say he is greedy and accepts. I should think that he dies in the story if not the next one.
Storyline
1. Major Villain plans revolt and brings Minor Villain to his side. Lets say, since he is from an outlying region, he has the support of a higher group of people from another kingdom.
2. He kidnaps the emperor's daughter and holds her for ransom
3. The Emperor's army comes along with his brother and they pay the ransom
4. Major Villain slaughters them and gains magical abilities
5. Major Villain offers Minor Villain magical powers if he kills the Emperor's daughter
6. Emperor's daughter escapes
7. The kingdoms is taken by Major Villain and the emperor is killed
8. The Emperor's daughter is taken in by a group of mountain people and then learns how to control her magic from them
9. She returns and takes back the kingdom
10. She becomes a wise and better ruler than her father and the people love her
11. Status Quo updated
>>MY BRAIN HURTS<<