Kristoffer Rygg (born 9 September 1976), also known as Garm, Trickster G. Rex and God Head, is a Norwegian vocalist, musician and producer known primarily for his work with Ulver, Arcturus, and Borknagar.

Rygg is also the former vocalist of Borknagar (1995–1997) and Arcturus (1993–2003), both of which comprise central musicians from the early Norwegian black metal scene.

In recent years Rygg has been involved in freeform/improvisational project Æthenor which includes notable musicians such as Stephen O'Malley of Sunn O))), Daniel O'Sullivan of Guapo and David Tibet of Current 93.

A year later, and after a series of shows around Europe, Rygg stood in front of a full house at the main stage of Oslo's National Opera & Ballet.

He has acted as guest vocalist, lyricist, engineer, producer, and remixer for a large list of artists, including Alkaline Trio, Mindless Self Indulgence, Genghis Tron, Darkthrone, Mayhem, Emperor, Ihsahn, Dimmu Borgir, The Gathering, Merzbow, Carpenter Brut and Sunn O))).