Yyrkoon (so named after an obscure character in Michael Moorcock's Eliric series) have experimented with a number of different metallic styles over the course of their still developing career. At first, the band brought an ambient dark/black metal sound to 1996's Oath, Obscure, Occult demo and 1998's Oniric Transition debut album; but problems with their record label effectively iced their career until 2000, when a three-track EP called Forgotten Past finally succeeded in securing a new deal with Anvil Records. By then, Yyrkoon's sound was best described as thrash-fueled progressive metal topped with fantasy and terror-inspired lyrical concepts and could be heard on their second album, Dying Sun, in 2002. This active period served to solidify the group's lineup as Stéphane Souteryand (vocals/guitar/keys), François Falempin (guitar), Voctproen Vilchez (bass), Geoffrey Gautier (guitar/keyboards), and Laurent Harrouar (drums), if not their musical direction, which shifted radically once again for their Osomose Productions debut, Occult Medicine, in 2004. Most any signs of gothic and dark metal ambience were now gone (as were the rather superfluous keyboards), and in their place left ever-greater aggression and a crushingly thick death/thrash metal assault. Surprisingly, these tendencies remained relatively unchanged for the band's fifth album, Unhealthy Opera, also released by Osmose in 2006.