"The problem with living a really long life, is that sometimes you outlive your star." A rogue planet tumbles through the cosmos; while its people desperately search for a new home in an alien system, before being jettison back out into space.
Secretly thriving for millions of years, the trilobite commands an ancient underground sea. When cataclysmic events threaten to end humanity, the trilobite will call on a select few to supersede modern existence.