[1] It is rooted on Norwegian black/Viking metal and experimental rock on some tracks, and named after the large fortress Isengard in J. R. R. Tolkien's The Lord of the Rings book series.
The person/creature in Isengard's logo was taken from an old Lord of the Rings RPG called Middle-earth Role Playing.
[2] When asked how he felt about Isengard in a November 2007 interview, Fenriz commented that he does not "understand why people like it so much".
[3] He stated that people like "the elements" which he doesn't like, namely the project's folk metal aspect.
A third Isengard album entitled "Vårjevndøgn" was released in October 2020, consisting of unreleased recordings from 1989 to 1993.