There are three artists under this moniker.

1. A Death Metal band from Copenhagen, Denmark.

2. A black metal band from Denmark.

3. An electronic music group from France.

1. This Kill-Town (also known as Copenhagen)-based rotten Death Metal trio started in the June of 2008, and has so far released 2 full-lenghts "Indhentet af Døden" and "Til Døden Os Skiller", a split album with Funebrarum and an EP.

A. Dødshjælp - Drums
K. Ondsind - Bass
D. Torturdød - Guitars / vocals

Links:
http://www.facebook.com/pages/Undergang/147478011999818
http://undergang.bandcamp.com/

2. A Dannish Black Metal band from the town of Skjern. Released one demo before splitting up. 'Undergang' is Danish for ruin/fall.

3. https://soundcloud.com/undergang Read more on Last.fm. User-contributed text is available under the Creative Commons By-SA License; additional terms may apply.