Idea: Alien Succubus Plays Cupid
So, here's a story idea I had, which, like all of 'em is available to anyone who wants it:
Thousands of years ago, a shapeshifting psychic alien is stranded on Earth. The hows and whys are not important; what matters is that she (for the alien is female) will not be going home, nor will others of her kind show up. She soon discovers that she can survive by feeding on the emotional energies humans produce during sex. For this reason, we will henceforth refer to the alien as the Succubus.
Since the Succubus can assume any shape, read minds, and does not ascribe to any sexual taboos, combined with high-levels of human horniness, it proves relatively easy for her to seduce a long string of people and get some sustenance. It becomes even easier when, after a century or three, she becomes a prostitute, ensuring a steady diet. However, prostitution brings with it repeat customers, from which the Succubus makes a discovery; while meaningless animal rutting provides enough to live on, when there is some measure of attachment, the result is both more filling and, for lack of a better word, more "delicious".
This suggests a new course of action, wherein the Succubus goes in for courtship rather than mere seduction. This requires more effort, but her natural abilities have since been augmented by a detailed study of human behavior, so it's not that hard, and the result is well worth the extra effort. Unfortunately, she also discovers that feeding on a specific human for a prolonged period damages them, often fatally. Being an ethical creature, the Succubus is unwilling to kill her prey, especially since the time and effort spent building attachment inevitably results in her becoming somewhat attached as well. And so, every few months, she leaves her current lover and creates a new identity, the knowledge that she has made him or her happy for a time insulates her from the emotional pain she has caused by leaving.
Then, she hits the jackpot, falling in with a man with a taste for group sex and a voyeuristic streak. Being able to spread her feedings out amongst the various partners he finds for her has allowed the Succubus to stay with him not for a few months months, but for three whole years. But all good things must come to an end, and the time is approaching where she must make her exit. Unfortunately, in those three years, the Succubus has become even more attached to her lover than she usually does, enough so that she cannot bear to causing him emotional. But she cannot stay without harming him.
For a day or three, she agonizes over this choice, before finding a solution; ensuring that by the time she leaves, he has someone else, a replacement who is in truth the perfect soulmate she pretends to be....
"An ape does not care about brownie points, gold stars, Olympic medals, or PHD diplomas. To a human, these things are more valuable than a whole shipload of bannanas. This makes us pretty dumb by ape standards."- Charles Whitehead.