Alternately hailed as a revelation or a betrayal, 2008's Assassins: Black Meddle, Pt.

1 is, like any musical watershed, a controversial and polarizing work.

Not that anyone has any reason to be surprised at its audacious creative direction given Nachtmystium's inexorable rate of evolution over the years, as they swiftly began embellishing their initially "trve" and "cvlt" black metal origins with ever more adventurous progressive and psychedelic elements by the release of third album, Instinct: Decay.

What's more, with numerous other black metal bands exploring similarly nontraditional influences throughout the '00s (e.g.

Enslaved, Agalloch, etc.), one has to assume that the real reason behind these scattered cries of protest from the Nachtmystium faithful is simple nostalgia for the sounds of triumphs past, rather than any actual beef with the latest "meddling" taking place on Assassins.

Chances are, though, that the vast majority of listeners will simply wonder what the fuss is all about when faced with suitably "blackened" opening snippet "One of These Nights" and its gale force winds, whispered incantations, and foreboding riff descended from Black Sabbath's "Children of the Grave." Even the ensuing eight-minute title track launches off a perfectly legit necro-battery of blastbeat-driven black metal before eventually engaging in everything from punk-simple rock & roll riffs to electronic sound effects as it runs its lengthy course.

Spacy electronics, gothic melodies, and hypnotic overtones continue to assail follow-up highlights such as "Ghost of Grace" and "Omnivore" -- the latter also being marked by oppressive low-end fluctuations reminiscent of industrial-tinged French outfit Blut Aus Nord.

On the other hand, both the back-to-basics black metal onslaught of "Your True Enemy" and the deliberately gentle drift of "Code Negative" (heavily indebted to Pink Floyd, if you even have to ask) feel more like good excuses for creative mastermind Blake Judd (aka Azentrius) and colleague Jeff Wilson to improvise rather self-indulgent, yet fittingly melancholic guitar solos.

And Nachtmystium's compositional thrill-seeking only escalates as they come to the album's closing "Seasick" trilogy, which contrasts crisp, angelic melodies against a more typically evil and bleary harmonic foundation for part one, "Drowned at Dusk"; whips out astonishingly jazz-flavored guitar leads and saxophone (yes, a saxophone!) for part two, "Oceanborne"; then commingles all of the above, plus shouted vocals recalling Floyd's "Nile Song," for the majestic third part, "Silent Sunrise." In the end, Assassins is over all too quickly, which says something about the lofty standards maintained throughout, and even more about the fruitless bellyaching surrounding its rejection of short-sighted, self-imposed black metal boundaries.

Honestly, if Nachtmystium carry on producing extreme music of this caliber, most open-minded listeners will surely agree that they can meddle all they want.