Twenty One Pilots take fans to the Upside Down with 'Stranger Things' and 'Heathens' mash-up

Kate Bush. Metallica. And now Twenty One Pilots.

The number of musical acts getting into the Stranger Things business increased by one at the Electric Castle festival in Romania last Friday when the Ohio duo treated fans to a mash-up of their 2016 hit "Heathens" and the Netflix show's synth-happy theme.

Their festival performance kicked off with the booming voice of Stranger Things big bad Vecna (Jamie Campbell Bower) as the Upside Down denizen tormented poor Max (Sadie Sink) in scenes from season 4 that played on massive screens at the back of the stage.

Vladimir Prycek/CTK via ZUMA Press Twenty One Pilots

When a clip appeared of Max's lifesaving headphones being slipped over her ears, Twenty One Pilots lead vocalist Tyler Joseph and drummer Josh Dun walked on stage beneath the words "Music has the power to save everyone."

They then launched into "Heathens," while the Stranger Things theme, penned by Kyle Dixon and Michael Stein, weaved in and out. Fittingly, the performance ended on a scene of Eleven (Millie Bobby Brown) exerting her power to vanquish Vecna.

The official Stranger Things Twitter account clearly approved of the tribute, replying to the band's shared video with, "This performance could save me from Vecna any day of the week."

Season 4 of the Netflix smash famously features two music-heavy scenes. (Spoilers ahoy, streaming laggards!) In the first, Max is pulled back from the brink of death by her favorite song, "Running Up That Hill" by Kate Bush, while in the second, Dungeons & Dragons fan Eddie (Joseph Quinn) shreds his way through an epic version of Metallica's "Master of Puppets."

The boost in visibility gave Bush's 1985 song new life, and it went viral across social media, eventually hitting No. 1 on the U.K. charts and No. 4 on Billboard's Hot 100. Meanwhile, Metallica later rocked out to a TikTok version of "Master of Puppets" in Hellfire Club shirts straight from the show.

This isn't the only entertainment link "Heathens" can claim — the song was originally released as the lead single for the 2016 DC Comics film Suicide Squad.

Stranger Things season 4 is streaming now on Netflix. The streamer has yet to announce a release date for Season 5. Check out Twenty One Pilots' Stranger Things and "Heathens" mash-up below.

EW's Ultimate Guide to Stranger Things is available online or wherever magazines are sold.

Related content:

• A beginner's guide to Kate Bush — for everyone who just watched Stranger Things

• Watch Metallica recreate Stranger Things' tribute to their 'Master of Puppets'

• Placebo goes 'Running Up That Hill' to remind us they once covered Kate Bush's song

• Stranger Things sets the stage for a Vecna-Eleven showdown in season 4, Vol. 2 teaser

• The Duffer Brothers on Stranger Things 4's big reveals, cameos, and why 'everybody is in jeopardy'