In April 2006, Tveitan released his first solo album, "The Adversary". He recorded and produced the album by himself, with the exception of drums which were contributed by Asgeir Mickelson, and guest vocals on the track "Homecoming" by Kristoffer Rygg of Ulver. The album showcases his progressive influences as well as heavy metal, black metal and classical music. "The Adversary" was recorded at Symphonique Studios in Norway and was released on his label Mnemosyne Productions, which he founded in 2003 with Starofash. A video was made for the opening track, "Invocation".