What is "isengard"

In J. R. R. Tolkien's fictional universe of Middle-earth, Isengard , a translation of the Sindarin Angrenost, was a large fortress. Both names mean " Iron fortress" (cf. German Eisen and Old English isærn = iron), though Isengard has a second meaning of "West Guard".

Isengard was a solo project of Fenriz, famous for being the drummer of Darkthrone, created in 1989.

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.