The new disc, titled "Senprūsija" (Old Prussia) even features two tracks with Old Prussian lyrics (including Rāmava, above), despite the fact that the language, along with the culture that gave it birth, has long been lost in the mists of time.
Members of the band, which has been together 20 years, even undertook a crash course in Old Prussian history with academic Agris Dzenis before beginning work on the latest disc, says lead singer Pēteris Kvetkovskis.
"The main basis of knowledge about the Old Prussians are the crusader chronicles of the 12th and 13th centuries," says Kvetkovskis.
"They had their own heroes, among them Herkus Monte, who was one of the great Prussian freedom fighters... Then there are other legends such as the story of the brothers Videvuds and Prūtenis who arrived from the north and laid the foundations of Prussia."
"The stories are tragic with fierce battles, so go very well with aggressive, heavy music," Kvetkovskis adds.
By the end of the 13th century, the Old Prussians were conquered as Germanic crusaders forcibly converted the ancient pagan Baltic cultures at the point of a sword. By the 18th century their language and culture had all but disappeared.
Nor is the parallel of a small, distinct culture fighting for its identity and very existence against a large, heavily militarized neighbor lost on the group.
"[The cover of the album shows] All that's left of the Prussians are bones, sand and dust," says Kvetkovskis.
"The Prussians prove how easy and completely a people can disappear from the pages of history. That's not to say they are destroyed, because the main reason for it was that they were assimilated into German society.. I think it is such a frightening example of how easily it can happen."
The album contains 12 songs, two of them heard in the Prussian language, though Kvetkovskis admits it is difficult to know exactly how authentic the sounds are as academic arguments rage over precisely who the Old Prussians were, what was their fate and to what extent remnants of their culture survive in the other Baltic cultures.
On 8 April Skyforger embarks on a European tour with concerts in Hungary, the Czech Republic, Germany and Portugal. the band returns home to Latvia in mid-May and is set to headline the "Sword and Ploughshare" festival of folk metal in July.