Zymosis were formed in the island of S. Miguel, Azores, on September 2001 by Ruben Medeiros and Rui Arruda, who decided to play a Black Metal influenced by Cradle of Filth, Dimmu Borgir, Emperor and Darkthrone. Later, the line-up was completed with Helder Medeiros as the vocalist, Bruno Pimentel on keyboards, Flávio Medeiros on drums, Bruno Dias on bass, and Bruno Carreiro on lead guitar, substituting Ruben Medeiros who left due to personal reasons.

The first release was a live promo entitled "Welcome To The Devil's Lair - Live Beside The Church", recorded at the 'Livramento Headbangersfest' festival. In 2004, the band is released a demo CD, "Disharmonical Symphony Of Black Dimensions".