A god is, by its very nature, immortal.
It is said that the faith of men sustains gods. This is a tale, made up by men to convince themselves of their own worth. Faith certainly increases a god’s power, for there are very few forces in universe as strong as the will of the faithful. But a god never dies. A god without power loses its ability to influence our world. This is not a terrible hardship for a god – it can always stay in its own realm, or find another world, or – if it still has enough power – start a whole new one. The realm of a god grants it no power outside of itself, because faith requires free will. Gods may be above men, but they are natural beings. They are immortal, but almost never omnipotent. The nature of power is will.
Faith is not the antithesis of knowledge. Men from worlds where gods do not manifest think that faith is the belief in a god’s existence, but there are many worlds and many men who know gods, who see them, feel their power – even their wrath – yet do not grant them power. Men think their faith sustains gods because a god’s power is the effect of the will of the faithful.
But you cannot kill a god.
When gods manifest, they have physical bodies. To hurt a god’s body is almost impossible, but it can be done. The body of a god is made of the will that its faithful did not get to spend. This is why gods like to send the faithful into war. If a man dies for his god, the faith becomes a channel for his natural will. The power is for the god to use as it sees fit. The remnant will is what some men call the soul.
The body of a god is made of the souls of his deceased faithful. No god is omnipotent, and no power is endless. The will of a man who died for his god is not for anyone but the god to use – it cannot be drained; but it can be destroyed. To hurt the body of a god is to destroy the souls of the faithful. Their will, their essence, is lost forever; they do not rest in the god’s realm, they are not reborn into a world, they never receive their eternal reward. They are simply lost forever.
That is why, even though you cannot kill a god, all gods are cowards.