I wish i had a context for this. But I really dont.

I was all ready to “um, actually” this, but, um, actually there’s about 3-4 grams of iron in a person, which x400 is 1.2-1.6kg, which is a smallish but not unreasonable sword. So. Math checks out.

How would you extract the iron, though? The more practical solution would be to kill a mere hundred men, then mix 1 part blood with 3 parts standard molten iron, imo. Cheaper and faster, while still retaining the edge that only evil magic can give you.

Or, you could just make the sword of iron, and then use the blood to temper the blade.