The Mikaelson family had a saying. "Love beyond family is the greatest weakness. We do not feel and we do not care." It was a code he lived by. So why did he save the girl? Klaus / Caroline.

He always considered love to be a weakness but when the Alpha male meets his wild untamed wolf match, Mystic Falls becomes the perfect field for two lost souls on the prowl. In a world where the supernatural exists, nothing is stronger than human feelings and soon Klaus and Caroline find out that some things you just can't fight forever. AU Meme

This was who she was. What she was. She was an Original. The Alpha of the Originals. The most powerful being to walk the planet. She was the Queen of the Heartless, and she left fire and death wherever she went. Dark Caroline, Role Reversal, Mystic Falls gang is the Originals, Mikaelsons are present day humans. Eventually Klaroline, Kennet, Stebekah Delena, Janna, Kalijah.