What can not be healed?

[Kileanna]

Dalindra wrote:

In a game I was in, I was able to save a NPC with great risks and sacrifices from my character. When we finished the adventure, the DM told me that the NPC was not supposed to have a happy ending, probably not even survive. Even though we saved the world from an apocalypse, saving that NPC is one of the most memorables things I remember.

You were not supposed to save him! The story was way more difficult without his sacrifice and there was a lot of flavor that was lost. But you got to do it, you knew the consequences and decided to risk it all by saving him. I think it was great. I didn't want you to feel railroaded so it felt right just going on with the story. And I regret nothing, the results were great and the story was even more meaningful and epic that way.

[Ravingdork]

Do what I did with my character, Hama. Just say your character has a genetic disease that is slowly killing him. Add debilitating side-effects to taste.

This is literally what my character's bio says in it:
...[Hama] started showing the first symptoms of motor neuron disease. The tragic disease slowly stripped her of her independence, ultimately leaving her permanently paralyzed and mute. Local clerics were unable to stave off the advancement of the disease, much less cure it, as it proved to be genetic in nature (it is literally part of Hama’s natural state).

Then, under her special abilities, she has the following:
Paralyzed Due to an incurable genetic disease, you have been left completely paralyzed. You cannot move, speak, or take any physical action. You are rooted to the spot, frozen and helpless. You may still take purely mental actions, such as casting a spell with no components, and friends can still move your limbs or carry you about. The above stats do not reflect this condition. This disease is not transmittable to others.

I can't imagine most GMs turning you down for making your character weaker, unless you go so far with it that it proves detrimental to the group as a whole.

[Samish Lakefinder]

I suggest you look at the AP Souls for Smugglers Shiv. It has several mechanics and situations that would be directly applicable to what you are planning. It may give you some good alternatives to killing off the NPC.