There are multiple artists with this name:
1) Excessum was a black metal band from Sweden. They formed in 2001 and released their first demo, entitled "Oblivion" in 2003. In 2004 they recorded both the "Bleed Eternally" rehearsal tape (Bleeding Art Productions) as well as the "Death Redemption" full-lenght album (Deathstrike Records, Tour de Garde, Bleeding Art Productions), which was released in 2005.

Read more about Excessum on Last.fm.