NIGHTSIDE was formulated in the city of Turku during the Spring of 1996 by drummer Beleth and guitarist Focalor, soon adding bassist Lord Paimon to round off the initial line-up. Initially the band was titled DARKSIDE but soon evolved into the more familiar title. In August 1996 lead vocalist Serpent was added and soon after second guitarist Wraith. With a turbulent history of them NIGHTSIDE underwent so many line-up changes only Beleth would stand as a founder member at the time of launching the debut 2001 'The End Of Christianity' album.

Lord Paimon would be the first to leave, replaced by four stringer Storm (a.k.a. Tommi Rantanen) in late 1996. NIGHTSIDE added keyboard player Duchess Mary in 1997 and with this line-up undertook their debut live gig in Turku at Christmas time. However, Focalor would leave, relocating to Germany, and NIGHTSIDE duly enlisted Desekrator as replacement. Duchess Mary then made her exit and NIGHTSIDE subsequently suspended all live activity. At this juncture Storm was deputising with VORDVEN, a position he took up full time in November 1998. The group pulled in Zyldja'h Daimos for recording of their inaugural commercial product, the 'Ad Noctum' EP released by the Northern Heritage label.

Further membership troubles assailed NIGHTSIDE as Desekrator bowed out in July 1999 and Serpent then left to concentrate on his other, rawer Black Metal act ANNIHILATUS rebilling himself grandiosely "Commander Serpent The Annihilator". With NIGHTSIDE activity in limbo, Beleth temped for both VORDVEN and ANNIHILATUS for live work. NIGHTSIDE returned with a completely revised roster for the first album, 'The End Of Christianity' issued by the Portuguese Sound Riot label. Joining Beleth and Daimos would be vocalist Shax and guitarist Diabolus Sylvarum. Beleth joined PILGRIMS OF TARTURUS in mid 2003.

Re-billed as 'Gurglenator', NIGHTSIDE guitarist Aki Järvinen founded GORETORTURE for a 2004 album 'Promised To Kill You Last... I Lied'. The NIGHTSIDE credited Daimos666 (a.k.a. Zildja'h Daimos) joined BARATHRUM in February 2005.