There are at least six artists called Abyssus:
1. Death Metal band from Athens, Greece formed in 2011. They have self-released a debut EP Monarch to the Kingdom of the Dead in 2012, a limited split tape cassette with Nocturnal Vomit on Chaos And Hell Productions, 2013, and a limited split CD with Morbider on Ablaze Productions in 2014. They've also made consecutive appearances on Greek Death/Grind Scene compilation CDs in 2012 and 2013.
Official facebook page: http://www.facebook.com/pages/Abyssus/144338552349700

2. Split-up Black Metal band from Poland, formed in 1993. A demo recorded in 1994 One Alone in Bloodstained Forest was released on tape casesette by Terror Propaganda in 2007.

3. Blackened Death Metal band from New Jersey, USA formed in 2008. They have one self-released EP The Intensivist, 2013.
Official facebook page: https://www.facebook.com/abyssusnj
Bandcamp: https://abyssus.bandcamp.com/

4. Black metal project by Mortem from Georgia, USA started in 2007. Using a session drummer, Draugr, a demo tape Death was released by Racheschwur Records in 2008. Later in 2008 it was re-released by Wolfsvuur Records limited to 66 copies. There also exists a 3 track promo called Promo I self-released in 2008.

5. Black metal project by Kvarthaan from Germany started in 2005. He has one self-released EP Demo 2008.
Official myspace page: http://www.myspace.com/abyssusblackmetal

6. Black metal project from Minnesota, USA formed in (unknown). He/they have one full length album on tape cassette Abyssus released by A Terre Records, limited to 25 copies released 2012. Very little information is known. Read more on Last.fm. User-contributed text is available under the Creative Commons By-SA License; additional terms may apply.