David Harbour Reveals the Surprise Link Between This 'Stranger Things' Prop and Arnold Schwarzenegger

Harbour took to Instagram to share the epic story behind the sword he used in a recent episode of the beloved Netflix series.

David Harbour is sharing the epic story behind the sword he wielded during a season 4 episode of Stranger Things. In a post shared to Instagram Tuesday, Harbour revealed that the sword was actually the same one used by Arnold Schwarzenegger in the Conan films.

"Nerd alert. The prop at the end of episode 9 is the Atlantean sword from the CONAN films. A lovely fan found a still of when it was established in ep 7 and used by an unlucky inmate who met an untimely death near the cells at the side of our gladiatorial pit," Harbour captioned a still of the sword in Stranger Things as well as a picture of Schwarzenegger using it in the Conan saga.

"The real excitement behind this however, is that the sword the incredible ST props department (reveal yourselves guys so I can credit you) gave me is THE ACTUAL SWORD used in the filming of both CONAN films," he continued, referencing the Austrian actor's iconic role in 1982's Conan the Barbarian and 1984's Conan the Destroyer. "It was heavy as hell, and such a tremendous honor to wield. @schwarzenegger - ready to accept your notes on my technique."

The final two episodes of the fourth season, released on Friday, have sparked plenty of '80s nostalgia, including with the use of Metallica's "Master Of Puppets."

In the two-hour season finale, Joseph Quinn's character put on an epic performance of the song to distract the deadly bats that were protecting the lair of villain Vecna. Shortly after the episode dropped, the 1986 song started climbing music charts in both the U.S. and U.K.

On Monday, "Master Of Puppets" landed at number 12 on Spotify's Top 50 U.S. chart and at number 26 on the music platform's Global Top 50. 

As for how much of the performance was Quinn actually playing guitar, he told ET, "It's pretty much all of me."

"I've played guitar since I was quite young, so I had kind of the foundations to take most of it," he explained. "It's great fun... Who wouldn't wanna kind of be a rock star for an afternoon or an evening?"

Metallica reacted to Quinn's performance and the "next level" use of the song in a post the band shared to Instagram Monday.

"The way The Duffer Brothers have incorporated music into Stranger Things has always been next level, so we were beyond psyched for them to not only include 'Master of Puppets' in the show, but to have such a pivotal scene built around it," the group said. "We were all stoked to see the final result and when we did we were totally blown away... it’s so extremely well done, so much so, that some folks were able to guess the song just by seeing a few seconds of Joseph Quinn’s hands in the trailer!! How crazy cool is that?"

Metallica continued, "It’s an incredible honor to be such a big part of Eddie’s journey and to once again be keeping company with all of the other amazing artists featured in the show."

Earlier this year, Kate Bush's 1985 track, "Running Up That Hill," enjoyed a similar level of newfound attention after it was used on the show. 

The singer reacted to the resurgence of her track in a post on her website, saying she was "really moved."

"The Duffer Brothers have created four extraordinary [seasons] of Stranger Things in which the child actors have grown into young adults," Bush wrote, referring to Matt and Ross Duffer, who created the Netflix series. "In this latest series, the characters are facing many of the same challenges that exist in reality right now. I believe the Duffer Brothers have touched people’s hearts in a special way, at a time that's incredibly difficult for everyone, especially younger people."

Season 4 of Stranger Things is streaming on Netflix.