Onmund was a student in the same class as Crotch Guzzler. He tried to get Crotch to get his necklace from Enthir.
Onmund did drugs with Crotch, and when Crotch inquired him on where he got his mushrooms, he replied, "The Mushroom Kingdom, man."
Crotch referred to Onmund and J'zargo as Cat-Man and The Faggot.
Onmund was eventually killed by Crotch like everyone else at the College of Winterhold. Crotch tried to cover up the murder by claiming that Onmund had fallen down the stairs, to no avail.