Astronomical observatories of an ancient civilization, architecture of a different planet, a labyrinth with a hidden library of esoteric literature, and the abstract realm of chaotic energy – these are examples of atmosphere induced by the album. This is an exotic album that takes the listener on a journey to the unknown lands – not just medieval castles, Viking ships, or dark forests infested with trolls, but something completely different. The power of this album to provide a wide variety of journeys lies in its eclectic nature; taking influences from various sources and employing a diverse arrange of techniques, Dark Millennium integrates them into a completely different monster called 'Ashore the Celestial Burden.' The music is closest to doom/death, leaning toward the death metal side (Amorphis, Sorrow, Ceremonium, etc.), but a thrashy feeling is present from time to time, as are some black metallic tremolo riffs, and an abundance of melodic leads can be found. The closest approximation would be The Chasm, since both bands incorporate diverse components to colorful effects on a foundation made of doom and death metal elements, and even some of The Chasm's characteristic melodic content can be traced to this album (the refrain of 'Beyond the Holy Fatherlands' is an example), though Dark Millennium has a significantly larger amount of doom. It is almost operatic in that the lyrics and the music are integrated, but the very richness allows the listener to experience an independent atmosphere.
The most visibly unique trait of this album is the vocalist. The vocals are closer to thrash metal vocals than death metal vocals in that they are mid-to-high-pitched and have a bit of clean feeling instead of being completely harsh. Thrash vocals would generally not be fitting to a mystical form of music like this, but fortunately the vocals are, while having the mentioned similarities, far from typical thrash vocals. The vocalist is a man but he sounds suspiciously androgynous. However, not in the least does he sound lame; the combination of male and female qualities into a single voice strengthens the inhuman and exotic character, and the style of singing, which is like a tormented priest incanting in vengeance, makes maximum use of this strange voice. Occasionally there are vocal effects, either natural or electronically altered, which change the voice to something completely different, or make the vocals come in from a different starting point for each phrase, giving the impression of demonic possession. The vaguely clean-sounding trait permits a greater control over the vocal melody and allows the lyrics to be clearly delivered – the rapid, rhythmic delivery of rhymed lyrics in 'Beyond the Dragon's Eye' is an exemplary usage of lyrical clarity, and the spellbinding final stanza of 'Inside the Sunburnt Thoughts of Frost' exploit the melodic tendency of the vocals well. The lyrics are told from a first-person perspective of imagine characters (often a Christian, serving a satirical purpose) with frequent use of apostrophe, and the vocal theatrics work very well in its effective delivery of the lyrics, especially the in the cases of sinisterly greeting "welcome home my son" part in 'Black Literature,' and the soft yet eerie clean vocals of 'Beyond the Dragon's Eye' which haunt the supposed second-person to whom the lyrics are addressed.
Even with the mystical qualities, the rather high-pitched vocals could sound out of place on a typical doom/death album with focus on bass-heavy riffing. This album, however, in addition to being atypical vocally, is far from typical instrumentally. There are certainly a large number of riffs played on the lower strings – the dark and slow power chord-based doom riffs with some chugging and the faster death metal riffs with a chaotic sense of melody are probably the most abundant forms of riffs. There are also some thrash-influenced riffs, some of which are chugged in a thrashy way but still contain phrases with melody bent toward death/doom at the end, while others consist of constant alternate picking in triple meter, sounding vaguely speed-metal. On the other hand, there are also tremolo riffs played with higher-pitched notes, which resemble black metal more than death metal in their clear sense of melody and comparatively slow pitch-change, and many lead-riffs of an eerie character, sometimes with heavy echo in the background atmosphere (see 'Wizardry Assemblage'), both of which are frequently supported by contrapuntal melodies played on another guitar. There are also short lead passages, which, elaborating on the melodic potentials of the riffs underneath, serve as a variation or a transition into the next riff. The bass generally follows the guitars, but the addition of acoustic guitars, most heavily present on 'Inside the Sunburnt Thoughts of Frost,' and 'Beyond the Dragon's Eye,' more than compensates for the simple bass line; the acoustic guitars are often used in homophonic conjunction with the distorted power chords for melodic clarification, and there are even acoustic guitar solos, either above distorted or acoustic riffs. Guitar solos, whether they are played on acoustic guitars or distorted guitars, are never blazingly technical, and slow for the most part. The melodies are never really dissonant, but a sense of uneasiness is maintained, and even a more relaxed and consonant melody will eventually twist itself into the shadows. Synthesizers are generally employed for atmospheric effect, providing bell tolls in 'Beyond the Dragon's Eye,' and the clashing steel percussion of 'Father Legatus – Of Symbols, Nature, and Birth,' but are also used to provide actually melody in some cases, most notably in the instrumental 'Disillusion,' and the middle interlude of 'The Atmosphere.' The instruments contribute to the theatrical effect; the aforetime mentioned final stanza of 'Inside the Sunburnt Thoughts of Frost' is supported by a build-up of shifting lead melodies connected to the end of a uniform distorted phrase, and the haunting singing of 'Beyond the Dragon's Eye' is accompanied by either a twisted melody played on top of low-pitched chords, together forming harmonic dissonance, or dark acoustic arpeggios. The general mood of the album, as a consequence of the diversity and individual melodies, is exotic – not simply oriental, though there are quite a number of oriental melodies (most prominently the acoustic solo of 'Inside the Sunburnt Thoughts of Frost') and while it is outlandish, it is not spatial. It definitely leans toward the darker side, but instead of being black, it displays a variety of colors – including dark red, dark blue, and deep purple.
Each song usually has little repetition and tends to progress in a linear fashion, though there are exceptions including 'Below the Holy Fatherlands' and 'The Atmosphere' with the chorus appearing twice, and 'Black Literature,' which has the chorus thrice repeated. However, even these do not repeat complete verse-chorus cycles; instead they have the refrains entering in different contexts, with lengthy intros and middle sections, and 'Black Literature' segues into 'Inside the Sunburnt Thoughts of Frost' through an ambient interlude, so the sense of repetition is not very strong. The combination of stylistic diversity and lack of repetition could easily lead to chaos – fortunately, that is not the case, but nonetheless this aspect does render the album less than ideal. Transitions are rarely awkward, though sometimes abrupt such as the "reinstatement of my senses" part of 'Black Literature,' but they lack a sense of necessity, and except for 'Beyond the Dragon's Eye,' with a distinctively dark mood and a nearly symmetrical structure (it winds out the opposite way it progressed in the first half, like A-B-C-B-A), each song's thematic unification is not strong enough to keep it as a clearly distinguished entity when viewed from a holistic perspective. Each song does remain coherent and has a sense of beginning, climax, and ending when heard by itself, but a riff from one song could have been on another, assuming that sufficient contextual care has been given. However, songs are far from meandering pointlessly, and the relaxed structure contributes to the journeying nature of the album in that songs flow naturally from one to another, and the atmosphere is varied yet consistent album-wise, since many of the diverse elements are not confined to a few tracks but appear throughout the album.
From the vivid to the abstract, 'Ashore the Celestial Burden' displays a variety of atmosphere, without ever falling apart into randomness. This is a work of melodic diversity, mystical character, and progressive, albeit slightly loose, structure. This ominous and arcane album is not glaringly weird, but genuinely unique.