Outside of Iceland, they are known among music collectors for their rare releases on Parlophone, sung in English and recorded in London for export.
The most famous of these is the 1966 EP Umbarumbamba, regarded as one of the rarest released records in the world[citation needed] and known to fetch prices into the thousands of dollars when a copy surfaces.
Formed in Keflavik in 1963 under the name Hljómar (literally "Chords"), they soon became popular in Iceland at a time when local rock music was a rarity.
In 1969 a number of Thor's Hammer members went on to form the prog-flavored band Trúbrot, which recorded four albums until itself splitting in 1973.
The group's collected work is featured on the anthology, From Keflavík, With Love, released in 2001 on Big Beat Records.