Question: Was Oystein "Euronymous" Aarseth a guitarist in the band or co-founder of the band Mayhem?
Sentence (from "Parabellum (band)"): According to writer Emilio Cuesta, Øystein "Euronymous" Aarseth—a musician associated with the early Norwegian black metal scene—has said Parabellum and Medellín's Reencarnación were both influential to his own band Mayhem.
Relevant evidence: Yes