Having merely scratched the surface of Solstheim, I have yet to acquire the legendary arrows. But for the longest time I wanted to nerf the **** out of them, so today I decided to check what quest was related to those arrows and see if I could change their effect without breaking any mission. To my surprise, I can't seem to find anything. My question is, are the ebony arrows of slaying really some quest-less insta-kill items?

It's true that they are not related to any quest, but they can kill practically anything.... unless the enemy is using Reflect.
They can be found here:

So it is true after all. Thanks for the confirmation, Pluto.
Time to change a certain enchantment.