[Azimaith]

In traditional mythology demons are usually found with a sword of some type. And yes, katars were used in the game diablo but those are hardly a great representation of what they are. Poison of some kind is always good, imagine a incorporeal decaying claw or sword. It passed directly through solid objects but when it hits flesh it the organic material decays extremely fast making even a touch with it extremely painful and deadly. (it will give ya blood poisoning not to mention the fact that the flesh will liquefy when its decaying.) That seems like a very demonic weapon to have, if not for the main character you could use it for one more evil. Still katars would work well.