After we reported on the ultra-rare Unique drop, players came forward with proof that has already been confirmed to have dropped, leaving only left to be found!
How to Obtain the Six Rarest Uniques Unique Drop Rate Community Opinions
The Rogue Shyanne aka ViZiOnZ333 has found the Sword around June 12. Unfortunately, we do not know where they found the Unique in-game. Content creator DonTheCrown shared the drop with the community on their Twitch stream.