It's fairly common knowledge that the Wookiee Chewbacca owed a life debt to Han Solo, the famous smuggler and Rebellion general. This life debt came about when Han saved Chewie's life when they were younger, when Han rescued Chewie from a life of servitude, torment, and a dragged-out death. Wookiee culture generally takes the life debt very seriously, and Chewbacca was no exception. He swore to stay by Han's side and protect him from danger. The two of them became fire-forged friends, where one would always have the other's back. Han even learned to understand Shyriiwook, the language of the Wookiees, so that he would be able to communicate with Chewie.

There's a less commonly known aspect of the Wookiee life debt, though. If the Wookiee dies of natural causes, then in Wookiee culture he is seen as having abandoned his obligation. The idea was that it would be shameful for a Wookiee to die of an illness or accident when they are such ferocious fighters. A Wookiee with a life debt should die, ideally, by sacrificing his life for the one he owes the debt to. Anything less than that, and you're supposed to stay with the person you owe the debt to, and do everything in your power to protect them. If you die of sickness or old age, then you're shirking your responsibility to your life debt.

This taboo against dying of natural causes has led to an interesting custom. If the Wookiee has fallen ill or is incapacitated by an accident, and recovery seems unlikely, then the Wookiee will ask the subject of his life debt to kill him. In part this is penance for failing to uphold the life debt, and in part this is to ensure that the Wookiee is concluding his life debt with full acknowledgement from the subject of the debt.

Han and Chewie had many adventures together throughout the galaxy. They helped Luke destroy the first Death Star, they fought together at Hoth, Han was encased in carbonite until Chewie helped free him, and then they went on to destroy the second Death Star together. Afterwards, they went on to accomplish many more feats, side by side as brothers, burnishing a legend that was already glorious.

Gradually, however, Chewie could feel himself growing older. Wookiees have a naturally long lifespan, but even a Wookiee as mighty as Chewbacca must reach the end of it someday. He'd faithfully stood by Han's side throughout all the events of their lives together, but now he knew he could not continue with his life debt much longer. So he sat down with Han in the galley of the Falcon, and had a very serious conversation with him.

"Han, my friend, soon you will need to kill me and release me from my life debt," Chewie growled in Shyriiwook.

Han immediately reacted with horror, "What? Chewie, no, I couldn't do that!"

"You must, it is the way."

"You're crazy! There's no way I'm going to just shoot you! I'm not going to just do you in like that!" Han declared as tears started welling up in his eyes.

Chewie sighed, then said, "Han, let me tell you what's going to happen if you don't. I'm going to get old, and sick, and then die. You're going to have to watch me go through the whole process. It's going to be long and painful for the both of us. And then, after I'm dead, I will be remembered as a pariah on Kashyyk. I'll be known as a Wookiee who got out of his life debt by dying by myself. Do you want that to happen?"

"No, but..." Han said, "But surely there must be some other way!"

"Well, I suppose I might recover my strength. Perhaps I'm not at the end of my life after all, and the worst will pass, and I'll be as fit as I was before," Chewie said with an air of skepticism, as he scratched his furry chin with one paw. "But even if I recover, this day will still come eventually. And there'll be no escaping it then. You'll have to see me old, and frail, and sick, and you'll still have to kill me. No, better for you to kill me now, while I still have some semblance of fitness left. Can you do that?"

"I can't!"

"Wouldn't you rather remember me as I am now, as a powerful and fierce Wookiee? Instead of waiting for me to reach my lowest point, and finally killing me then?"

"Well, sure... but I can't just do you in now! I just can't!"

Chewie sighed again, then said, "Very well. If you can't, Han, do me at my worst. Then, you don't preserve me at my best."