Brooklyn's Orthopedic Cranial Encavement announced themselves in 2021 with a name that functions as its own content advisory — a grindcore act whose music is as compressed, chaotic, and medically inadvisable as their moniker suggests. New York noise colliding with blast-beat precision.

La Crosse, Wisconsin's Orwell have been churning out melodic death metal and metalcore hybrids since 2000, weaving sharp melodic leads through abrasive, groove-driven riffs. Their sound sits at the intersection of Scandinavian melodeath sensibility and American hardcore aggression.

Oscuro Mito is a black/folk metal band from Cochabamba, Bolivia, formed in 2008 and released through Catáfila Producciones. Their music draws heavily on Andean themes — Inca and Aymara culture, ancestral legends, and indigenous paganism — which sets them apart within Bolivia's extreme metal scene. The band released their debut full-length Yuraq Ushpa in 2019, following years of demos and split appearances including the 2015 compilation Holocausto Zine.

Named for the ruined city at the heart of Tolkien's Middle-earth, Osgiliath conjure a desolate black/doom sound that mirrors their namesake — crumbling, ancient, and saturated in dread. Active since 1996, their music unfolds like a slow descent into shadow.

OSI (Office of Strategic Influence) was an American progressive rock and metal project formed in 2002 by Fates Warning guitarist Jim Matheos and ex-Dream Theater keyboardist Kevin Moore, who described their aim as bridging progressive metal and electronica — two genres he called 'almost natural enemies.' The project released four studio albums — Office of Strategic Influence (2003), Free (2006), Blood (2009), and Fire Make Thunder (2012, Metal Blade Records) — featuring rotating contributors including Mike Portnoy and Gavin Harrison on drums. OSI operated largely as a remote studio collaboration, with members tracking material independently before coming together for final assembly.

Fort Lauderdale's Osiris Rising bring an atmospheric weight to traditional heavy metal, drawing on mythological grandeur to color their dense, reverb-soaked sound. Formed in 2025, they're one of Florida's newest acts staking a claim in the atmospheric end of the genre.

Ospetor is a raw and atmospheric black metal project from Loja, Ecuador, formed in 2020 and operating under strict anonymity — no names, no identity, no ego. Their 2020 debut Demo I, recorded at Umbral Xtudio/Dungeon Rec, delivers visceral and primitive black metal rooted in the virulent South American underground tradition. Released through Sutsircitna Productions, the band draws comparisons to acts like Satanic Warmaster for their uncompromising, trance-inducing approach to the genre.

Cincinnati's Ossification channel raw, uncompromising black metal with the grim intensity you'd expect from a band formed in 2023 and already committed to stripping the genre down to its harshest essentials. Cold, relentless, and unapologetically underground.

Ruthless Black / Death Metal out of Texas.