Well, let's face it; while this "dark princess" is not inherently evil, her parents ARE...and they had been killed, by now. (And no; she's NOT related to that other fairy princess, Aina. And she's not even related to the same man, that the other one fell in love with Aina, either!)
Her name's "Nyx Diamondblood".
This princess has been sent to a dungeon, for the safety of herself, and innocents. Thing is, she's also replaced, in a tech restraint kit, in the middle of a room, because she is dangerous.
The good side of her is simple, to explain; she respects the poor, to some extent, she doesn't believe in torture, (saying that it's stupid, and otherwise, not in her nature) and she always managed to be charmed, by wildlife; even spiders, when they fist hatch.
She's part elf, (from her father's side) and part fairy. (from her mother's side) Her wings aren't shown, because they are broken; while her wings are broken, and forces of good, have taken over the kingdom, many of such guards that are recently hired, wanted to treat her with kindness; saying that, she's not ready, for the throne; at least not yet. In addition, they had to put such wings, in a cast, until then.
Luckily however, they're nice enough, to treat her with respect. In addition, there may be a young man, that needs her...there are also some sad things that happened in her past. If one is to change her heart, that someone has to be there for her; as a true friend, in need...that's why if she were to leave that room, she'd need someone nearby, to look after her...and make sure, that she doesn't try to make a run for it, so she an start doing something sinister.
= Nyx, alongside the artwork, are (c) by me