I have the info on the sword. I am sure you would not like part of it. From memory you attuned to it. The spirit in it is one of vengeance. You are unwilling to part with the sword.
You also have diadvantage on attack rolls with other weapon! I believe I reworded that to apply if you did NOT attack with this blade in the same round. ie another weapon in off hand is okay.
Also, when hit you have to pass a save when hit.
Anyway, look in DMG p206 at the sword of vengeance. That is what it is . From memory I said just look it up at end of last session.
However, I still do not know where I got the pic from ;) I will keep looking.