With 666 International, Dødheimsgard abandoned the black metal style of their previous two albums, further developing the style of their EP Satanic Art (1998). The album heads into a more avant-garde style that fuses black and industrial metal, with some electronic and keyboard interludes.
666 International was Dødheimsgard's last release to feature Aldrahn on vocals (until his eventual return to the band in 2013, when the band recorded A Umbra Omega with him), Apollyon on bass, and Svein Egil Hatlevik on keyboards. It was also their last release under the name Dødheimsgard; in 2003, the band shortened their name to DHG.
The piano intro on "Shiva-Interfere" is taken from the outro track "Wrapped in Plastic" from Satanic Art.
It was re-released in 2011 by Peaceville Records, and included two bonus tracks. "Hæmorrhage Era One Reconstructed" was originally featured on the 2000 compilation Moonfog 2000: A Different Perspective.