A new extreme metal festival is officially entering the chat.
Flatline Fest, curated by producer Dave Otero (Flatline Audio), will make its debut this summer as a two-day blast of technical, brutal and experimental metal in Denver.
The festival takes place June 13–14, 2026 at the Oriental Theater in Denver, Colorado, and is presented by Otero alongside co-promoter Chelsea Lowe. The lineup reads like a producer’s dream booking sheet — because that’s exactly what it is.
Otero explains:
“I’ve collaborated with every band in this lineup in the studio over many years and have always wanted to put something like this together. The fest is a chance to celebrate those friendships in one of our favorite independent venues.”
The first night will be headlined by Archspire, while Cattle Decapitation will close out the second night. Between them sits a lineup that balances precision tech-death, brutality, and Denver’s own extreme underground — with one particularly intriguing addition.
Nuclear Power Trio will be making their first-ever live appearance at the festival. The masked band has been the subject of endless speculation regarding its members (rumored to involve musicians from Allegaeon, Havok, and Cephalic Carnage), but confirmed identities aside, the group’s live debut alone makes Flatline Fest a notable event right out of the gate.
Flatline Fest 2026 Lineup
Day 1 — Saturday, June 13
Archspire
Aborted
Nuclear Power Trio (live debut)
Inferi
Of Feather and Bone
Clusterfux
Day 2 — Sunday, June 14
Cattle Decapitation
Allegaeon
The Zenith Passage
Cephalic Carnage
In the Company of Serpents
Necropanther
Tickets are on sale now, with weekend passes at $95 and single-day tickets at $50 (plus fees). For a first-year festival featuring this level of talent, that’s a pretty aggressive value proposition — and probably not one that’ll stay this affordable forever.
If Flatline Fest survives year one (and with this lineup, it probably will), Denver may have just gained itself a new annual extreme metal institution.
