As the title says, I've been trying to find the name of this book forever. I read it about 15 years ago. It's probably from the 1980's. The book is about a girl who for reasons I don't remember is connected to these two "light" beings from another dimension. They are able to siphon energy of some sort and give it to her making her immortal. These beings start off as children but by the end of the series they reach puberty and it becomes important that they get back to their home dimension. The girl girl is 12 years old but through the manipulation of these beings, she gets the body of an adult. She has a relationship with a ship captain. At some point she allows herself to age naturally, but then with the help of the energy beings, she reverts back to a young adult. I vaguely recall a god of luck and there may have been a "chained-god" and others. The antagonist at the end of the series is (I believe) a ship that wants to become a god or become mobile or something like that. I seem to recall a vampire making an appearance. If anyone has any ideas and/or leads to this book, i would greatly appreciate it.