Taken from Encyclopaedia Metallum:

Throne of Katarsis, keeping the early Norwegian black metal torches burning.
The Three Transcendental Keys aren't representative of flickering wisps of a burning husk, nigh on extinguished from a slight breeze, these torches spark new life, a resurrection of the old and forgotten. These Three Transcendental Keys illuminate even the darkest paths, as a beacon all shall see.

Somewhere along the way, Norwegian black metal lost its way. Whether due to an over saturation of bands, and people’s first ‘go to’ bands were all of the same order, meanwhile bands from other countries were merely shelved, and eventually people were just fed up with nearly every band hailing from Norway and began to look elsewhere? Admiringly, Throne of Katarsis have now carefully crafted four full length albums since their inauguration in 2002, slowly mastering, deepening and growing their spell craft on each subsequent release to ensure Norwegian black metal should be revered once again.

As dark, dank and mysterious as catacombs and their ancient chambers, Throne of Katarsis have prepared their altar to near perfection. Each track, a key to spell tomes, woven into the dense auras created from these lengthy incantations, throw woe and anguish spiraling into the air amidst overtures of guitars, before transcending into a vast vortex of somber chants and nostalgic screams, briefly echoing amongst the rising pulse of the drums and chiming of symbols. A convoluted bass becomes whorled amongst the projections, and The Three Transcendental Keys have performed their initial duties.

Whilst this is traditional Norwegian black metal by sound and production, Throne of Katarsis excel in fusing grandeur and creativity. Sweeping guitar melodies carry the tracks from one expanse to the next, seamless and consistently imposing their malevolence.
Though even by black metal standards, tracks at 11, 15 & 20 minutes can be a burden for some, and could have easily been dissected into 6 or 7 tracks instead. Such an array of high caliber song crafting however, ensures no moment is lost during the vast expanse of conjuration and performance. Whilst this is also Throne of Katarsis’ most varied album to date, adding a slower, more dynamic level to their creations, the velocity and furious rigor still remains.

True Norwegian black metal may be a shadow of its former self, and Throne of Katarsis only add small elements of new life to the genre, but they’re reason enough to have confidence that Norway can once again be renowned for black metal, and not have to rely on those early nineties bands to hold the flame.
Not exactly groundbreaking, but this is undoubtedly Throne of Katarsis, and their Three Transcendental Keys shouldn't go unnoticed.