You've been tricked! Due to [backstory] and [events related] you have found yourself immortal, with total control over the natural world around you (think Earth bending and stuff) and it's not all it's cracked up to be. You rocked around the world for a few hundred years performing miracles and being awesome until you realised that everyone you knew has grown old and died. People think you're a legend, like Bigfoot or Shania Twain, and you give up the spotlight and try to find some peace. But you're immortal too...
Cut to 43,000 years later and the world is unrecognisable, but you're still there. Looking... stretched but still youthful.
How much could you possibly remember about your past? How little would you care about current events knowing that you'd still be there no matter how it turned out? How can I motivate this character to help the hero?
Assume that anything goes, but no modern technology (I know 43,000 years and still stuck with High-Fantasy technology, get your act together imaginary world.)