BETRAYER was formed in Slupsk during 1990 as an agressive Thrash Metal band. That same year the group recorded an improvised studio demo tape 'Forbidden Personality' with Molly on both drums and vocal. Subsequently joined by ex-SLAUGHTER vocalist / bassist Berial the band adopted a fresh Death Metal stance. In 1991 BETRAYER recorded at CCS Studio in Warsaw a six track demo billed 'Necronomical Exmortis'. These sessions featured the late guitarist Morris and subsequently distributed through Carnage Records. That year BETRAYER performed at the 'S'thrash'ydlo' festival in Ciechanow and the 'Death Metal' festival alongside MESSIAH, GRAVE and MORGOTH in in Zabrze.

BETRAYER pulled in new guitarist Ripper, another ex-SLAUGHTER player. For a period in late 1991 Berial joined VADER as bassist. A further membership change in the BETRAYER ranks saw guitarist Northon replaced by Ryju. At this same juncture Northon, together with Molly, joined another Death Metal act CONDEMNATION.

BETRAYER activity on the domestic live front included shows such as a 1992 support to CANNIBAL CORPSE and SINISTER in Bydgoszcz, the 1992 'Shark Attack' festival, the 1993 'Metalmania' festival in Zabrze with THERION, MESSIAH, CANNIBAL CORPSE, CARCASS and DEATH and the 1994 'Metalmania' event sharing the stage with SAMAEL, UNLEASHED, CANNIBAL CORPSE and MORBID ANGEL.

In January 1994 BETRAYER recorded the 'Calamity' debut album at Modern Sound Studio in Gdynia for Morbid Noizz Productions. With the band's demise both Molly and Ryju joined MORTIFY.