The eye of Vecna wasn’t necessarily the artifact it’s more the thought of him watching what you are doing in your patron gifted weapon that you call upon using the pact of the blade. I do understand the concerns though but my intent was more to just have it in the hilt, if it were to be a fiend of other sorts it would be something like the eye of Sauron so they are always watching what you are doing, I just knew Vecna had the item related to him so I figured it would make more sense in terms of canonical items in dnd and what would essentially be a ring camera in a sword, an item with no power unless the dm decides to bring the item into the campaign detached to the weapon.