The Scientific Fact
When archaeologists cracked Tutankhamun's tomb in 1925, they were astonished to find a 3,000-year-old dagger which hadn't rusted. They were even more astonished not to find it in their back after saying, "See? The curse was nonsense!" It seems Egyptian burial customs preserve weapons of war instead of protecting mummies from (well-educated) thieves. Which isn't the most subtle moral, but nothing on Earth is less subtle than a pyramid.
I - like - big - BLOCKS and I cannot lie.
X-ray fluorescence spectrometry matched the blade's metal with meteoric iron. Tutankhamun was buried with a meteorite dagger, which makes Valyrian steel look like a letter opener. Maybe that's the only thing that can kill mummies. It also demonstrates the biggest problem with fantasy weapons: If there is a priceless relic weapon, in reality, the fabulously rich ruler of the totalitarian kingdom is much more likely own it.