Question: Hellhammer was a Swiss extreme metal band from Nurensdorf, active during 1981–1984, in June 1984, Hellhammer disbanded and founded another highly influential band, which Swiss heavy metal band, from Zürich?
Context: Triumph of Death is a demo tape by the Swiss extreme metal band Hellhammer.  It was released in July 1983.  It was recorded by producer Rol Fuchs in the band's rehearsal room on portable equipment sometime in June 1983, along with the material for the unreleased "Death Fiend" demo.  The two demos were typically combined into one, simply called "Triumph of Death".  Along with Hellhammer's other demos, it had a major influence on the emerging death metal and black metal genres. Death Fiend is an unreleased demo tape by the Swiss extreme metal band Hellhammer.  It was recorded in June 1983, along with the "Triumph of Death" demo, and later appeared on the compilation album "Demon Entrails". Ceremonial Oath is a Swedish extreme metal band who formed in 1989 under the name "Desecrator", changed their name to Ceremonial Oath in 1991 and disbanded in 1995.  During their short career they released three demos, one EP and two full-length albums.  Their influence is greater than their short lifespan suggests: several of the band members would later create or join metal bands that would gain fame and fortune on the future metal scene, such as In Flames, an influential band to the melodic death metal genre; and Hammerfall, a band who would greatly influence the awakened interest in power metal and traditional heavy metal. Triptykon is a Swiss extreme metal band from Zürich, formed in 2008 by Thomas Gabriel Fischer, founding member of the pioneering heavy metal bands Hellhammer, Celtic Frost and Apollyon Sun.  Fischer announced his departure from Celtic Frost in May 2008 and shortly afterwards revealed his new project would be entitled Triptykon. Eparistera Daimones is the debut album by Swiss extreme metal band Triptykon, the most recent musical project of Thomas Gabriel Fischer, founding member of the pioneering heavy metal bands Hellhammer and Celtic Frost and industrial project Apollyon Sun. Satanic Rites is the third and final demo tape by Swiss extreme metal band Hellhammer.  It was recorded and released during December 1983.  Along with Hellhammer's other releases, it had a major influence on the emerging death metal. Hellhammer was a Swiss extreme metal band from Nurensdorf, active during 1981–1984.  They are regarded as a key influence on black metal, and one of the founders of death metal.  In June 1984, Hellhammer disbanded and founded another highly influential band, Celtic Frost. Celtic Frost ( ) was a Swiss heavy metal band from Zürich.  They are known for their strong influence on the extreme metal genres.  Formed in 1981 as Hellhammer, the band became Celtic Frost in 1984 and was active until 1993.  It re-formed in 2001 and disbanded following frontman Tom Gabriel Fischer's departure in 2008.  The band was inspired by heavy metal groups such as Black Sabbath, Judas Priest and Venom, but also by gothic rock acts like Bauhaus, Siouxsie and the Banshees and Christian Death, and by the hardcore punk group Discharge. Apocalyptic Raids is an EP by the Swiss extreme metal band Hellhammer.  It was recorded and released in March 1984, and was the band's only commercial release. Jan Axel "Hellhammer" Blomberg (born 2 August 1969) is a Norwegian heavy metal drummer.  He is best known as the drummer of Mayhem, which he joined in 1988.  In 1987 Blomberg formed the avant-garde black metal band Arcturus (under the name Mortem) with Steinar Sverd Johnsen, which broke up in April 2007 and reunited in 2011.  He named himself after the Swiss extreme metal band Hellhammer.  Praised as a talented musician, Blomberg is a three-time winner of the Spellemannprisen award.
Answer: Celtic Frost