What is "grimborg"

Grimborg is the third studio album by Gjallarhorn, released in 2003.

The Allmusic review by Chris Nickson awards the album 4.5 stars and states "There's nothing like the pleasure one can get from hearing a band take a quantum leap in its development, and with the very purplish Grimborg (just look at the cover), Gjallarhorn has made theirs."