The band was formed at the beginning of the members' sophomore year, around 2006. They practiced together faithfully in Eric's parents' garage every week. Since Eric is friends with the owner of the Alto Bar, the band is able to play there any Saturday they want during its all-ages night, despite the fact that they, in the beginning, kept changing their name and couldn't be counted on to draw a crowd.
One of their biggest fans was Maureen Brown, a groupie of the band mainly because of her crush on Simon, before she was turned into a vampire. The band also once took in a new addition to the band, a werewolf named Jordan Kyle, before his death.
The band took on the name "The Mortal Instruments" in 2008 upon Simon's suggestion. In tribute to Jordan, the band mixed parts of Jordan's demos into the eleven-minute, primarily instrumental, song "Beati Bellicosi". This was Simon's final recording with the band and is considered among their best work. When Simon left New York, the band continued with Eric as the frontman and is known for its wild onstage antics. The band, still based in Brooklyn, has since made a name for itself, having fans and band merchandise even in Los Angeles.
Simon's band always changes its name and the members cannot seem to pick one to stick with. The many names, including those mentioned, suggested and mulled over, are (listed in order of mention):
- In a hallucination Simon had in Edom in City of Heavenly Fire, his band had just played a gig with Stepping Razor, a seemingly popular band in the series. First mentioned as a band Clary was listening to in City of Bones, the band is in fact a reference to Tithe: A Modern Faerie Tale, written by Cassandra Clare's friend Holly Black, wherein Stepping Razor is the band of a character, Ellen Fierch.