Nocturnus............... ARE AMAZING!!!!
I checked out The Key and it hooked me immediately.... really cool style, interesting keyboards, and the guitarists shred non-stop throughout the album..... they are definately one of the best duo's ive ever heard, the Key must have about 5000 solos on it..... so definately check it out immediately!
Their next album, Thresholds, jacked up the complexity and atmosphere, the solos and riffs are even more complex, its more melodic, another awesome album, "Arctic Crypt" is my favorite Nocturnus song....
They then broke up, but briefly reformed again in '99.... they released their final album "Ethereal Tomb" before breaking up again.... this album is awesome as well, it shows a slightly different side of the band, darker and more atmospheric than before, the keyboards are integrated better, the songs seemed to be more well thought out, and the guitar solos are still awesome.... plus theres lots of noticible improvements like the drumming, production, etc....
I highly recommend checking out all three albums.