Philadelphia's Horrendous employ a lethal mix of uncompromising grindcore and black, doom, thrash, and progressive death metal. The group's 2012 debut, The Chills, was rooted in traditional death metal. Subsequent efforts, including Ecdysis (2014) and Idol (2018), adopted a more progressive approach, eliciting comparisons to American death metal pioneers Death. Horrendous continued to refine their sound on 2023's Ontological Mysterium, matching sonic might with technical prowess.