180-gram black vinyl. 'Hydra' is the sixth studio album by Dutch symphonic metal band Within Temptation. It was originally released on January 31, 2014 in Europe and on February 4, 2014 in North America. The album contains guest appearances by singer Howard Jones (ex-Killswitch Engage), rapper Xzibit, metal vocalist Tarja Turunen (ex-Nightwish) and alternative rock singer Dave Pirner (Soul Asylum). It was the first album by Within Temptation to be recorded with three guitarists, with Stefan Helleblad making his Within Temptation studio debut on 'Hydra' since his addition to the band shortly after the release of 'The Unforgiving' in 2011. 'Hydra' is also the first Within Temptation album to feature Robert Westerholt's growling techniques since the band's debut album, 'Enter' in 1997. The band wanted it to be a real Within Temptation record, but heavier, more musically challenging, pushing borders and frontiers with new elements and influences, and at the same time bring back more from their early metal roots "... A bit like the past and future at the same time" - as stated by the band. The album title refers to the great variation in musical genres, the band improves on with each new release. Guitarist Robert Westerholt adds: "Hydra is a perfect title for our new album, because like the monster itself, the record represents the many different sides of our music". According to the ancient Greek mythology, the Hydra was a giant multi-headed serpent that, for each severed head, sprang forth two more in their place.