What do you mean by "make your PC or NPC immortal"?
There is no peace, there is anger.
There is no fear, there is power.
There is no death, there is immortality.
There is no weakness, there is the dark side.
I do not have fear, but rather I instill it in my enemies.
I am the heart of darkness.
I am the fire of hate.
I am the destroyer of worlds.
I know the power of the dark side.
All the universe bow before me.
I pledge myself to the darkness as I rule the Sith.
For I have found true power in the death of light.
-The Code of The Sith Lords