The female writer of "Eyes of the Insane" and Marcus Mumford were both musicians.
Toms Enrique Araya Daz (born June 6, 1961) is a Chilean American musician, best known as the vocalist and bassist of the American thrash metal band Slayer. 
Marcus Oliver Johnstone Mumford (born 31 January 1987) is a British-American singer, songwriter, musician and producer best known as the lead singer of the band Mumford & Sons. 
 "Eyes of the Insane" was written by vocalist Tom Araya during pre-production for the album. 
