Cifer is a speed and thrash metal one-man project from São Paulo, Brazil, formed in 2018 by multi-instrumentalist Henrique Perestrelo, who has also played in bands such as Blasthrash, Flagelador, and Infected. The project draws on 80s and early 90s influences including Exodus, Kreator, Sodom, Accept, and Mercyful Fate, and released the debut album "The Summoning" in 2019.

Cihoze is a Brazilian death/thrash metal project based in the Brasília/Goiás area, formed in 2020. The duo — Igor "Skullthrash" Gomes on guitar and vocals and Iury "Stringbreaker" Morais on bass and drums — released their debut album "Pesadelo da Realidade" in July 2020, recorded at Witchtrap Studios in Brasília.

Cinical is a groove metal band from Mendoza, Argentina, founded by brothers Vaka and Bruno Allegretti alongside Warren Marino and Uriel Memoli. Their album Resurgir was produced by Andrés Giménez of Argentine metal legends A.N.I.M.A.L., giving the record a heavy, mid-tempo groove rooted in the Mendoza underground scene.

Cinnamun Beloved is a gothic metal band from Buenos Aires, Argentina, fronted by vocalist and keyboardist Sabrina Filipčić. The band released their debut album The Weird Moment in 2015, followed by Stain in 2018, blending gothic metal with symphonic and electronic elements in a style shaped by the Buenos Aires underground.

Cipriano is a raw black metal band from Curitiba, Paraná, Brazil, drawing on the primitive, speed-driven style of acts like Darkthrone, Judas Iscariot, and Satanic Warmaster. The project features members active in the Curitiba underground scene and released the demo "Servos de Berwick" through Balrogh Records, with lyrics entirely in Portuguese.

Circadia is a heavy metal and hard rock band from Catriel, Río Negro, Argentina, drawing on classic 1980s and 1990s metal influences. The band has released recordings including the singles Leonidas and the EP Sucesos, building a following in the Patagonian underground metal scene.

Circulo Negro is an independent black metal band from Itaituba, Pará, Brazil, formed around 2013–2014. The band explores themes of witchcraft and satanism and released the demo "Supremacia Herege" in 2015, distributed through Brazilian underground distros such as Jazigo Distro.

Clamatorius is a black/death metal band from Goiânia, Goiás, Brazil, originally active from 1999 to 2005 under their own name after an earlier incarnation as Postumus (1998–1999). The band is notable for fusing extreme metal with Christian lyrical themes and released the five-track album "Consummatum Est" through Blackened Label Records.

Clan dos Mortos Cicatriz is a death-punk band from Curitiba, Paraná, Brazil, blending raw black metal, death metal, and hardcore punk into what the underground has called "nekro-hardcore." The band released their debut album "Técnicas de Morte" in March 2025 via Sentient Ruin Laboratories, a 15-track, 25-minute record described as a grim manifesto drawing imagery from slums, prisons, morgues, and war zones.