Love was usually not something you'd associate with the patron of theives. But there are always exceptions, and the Daedric Prince Nocturnal had found her highness in love with a mortal, or at least a mortal of Daedra standards. This mortal, however, was no average human. This was Leina; Dovakiin, slayer of Alduin World-Eater, Vampire Lord, Hero to Skyrim and all of Tamriel.
Nocturnal had observed several other Dragon-borns before. She always kept a watchful eye on them, seeking to claim whichever ones seemed fit of her blessing. She had found a few before, and they all proved their worth as excellent theives and assassins, but this one was different. She stood out to him for some reason, in a way that no mortal ever should.
But still, as impressive as this high-elf was, Nocturnal experienced what she thought was sorrow. Athough she wasn't sure, because no prince was ever sure of their emotions. He knew that Leina would never understand how she felt for her, and she knew that he could never share mortal love with her. She felt a deep rage of emotions inside of her vast soul, and couldn't begin to identify which ones she was feeling. She wanted to keep Leina, but was also slightly ashamed of feeling emotions toward her, or any emotions at all. She felt a strong desire burning for her, but yet also felt a confusion, not quite being able to pinpoint her feelings.
So Nocturnal did nothing, for if she acted she felt she would do the wrong thing. She instead watched Leina, studied her, every hour of every day; she looked over. In moments where it looked as if she were going to die, she would move something in her favor to keep her alive. She would not watch her suffer and die. She would never forgive herself if her soul were eternally cast into Sovngarde; far beyond her realm, where she could no longer watch over her, and where she would forever be a mortal; dead of a mortal's death.
Besides, what Daedric Prince feels mortal feelings for a mortal? It was all just too confusing, too aggravating, but yet also oh-so enjoyable. Nocturnal kept Leina close to her, watched over her and her choices. She could not interact with her like she deserved, so she came up with a plan to one day meet her, and they would fall in love, and Nocturnal could use her divine powers to make her a prince, as she rightfully deserved. But the timing had to be done just right, he had to find the perfect moment to enter her life.
And so Nocturnal waited, and watched, for the mortal Leina.