Beast

Beast (ビースト) is a non-standard Servant class populated by the seven entities classified among the Evils of Man (人類悪) -- the common designation for the Beasts of Calamity (災害の獣). It is for the purpose of acting as a fail-safe (安全装置) by which to counteract the Evils of Man that the Seven Servants of the Station of the Crown (七つの冠位クラスのサーヴァント) are summoned forth.

Overview
The Evils of Man are, as the name implies, the Stigmata of Humanity (人類の汚点) -- the seven Calamities (災害) positioned to enact the annihilation of Man; that threaten the continuity of the history of Man. Being entities that obtain standing within the World of the Primates (霊長の世) by way of factors that grow forth from human society and the Common Sense of Man (人理), the Evils of Man are existences that accumulate strength in proportion to the advancement of Man, and are in essence as cancerous cells that consume Humankind (人類種) from within. Empowered by civilization itself, they are beings that consume civilization -- the embodiments of the destruction visited upon the works of Man.

Rather than Servants brought forth via the evocations of spells founded upon "the Combat Ritual For the Salvation of the World" (世界を救うための決戦術式) -- "the Summoning of the Heroic Spirits" (英霊召喚) -- the Beasts are the original beings that came to accumulate spiritual stature (霊格) as Saint Graphs (霊基) ; the basis and archetype of the Heroic Spirits, which by the causality of self-inflicted karma come to act as a system for the of Man (人類の機構). That is to say, the exceptional capabilities or nature that Heroic Spirits exhibit when summoned as Servants are justified upon the same mechanics that lend the Evils of Man their capacity for threat.

Though the Beasts can be said to preside over the Seven Sins of Humanity (人類の七罪), the sins that they represent are not upon the death of. Rather, these "sins" come of the attributes that humans embody in existing as humans; those things that cannot be set aside so long as humans continue to subsist as creatures possessed of Wisdom (知恵持つ生き物). Being existences that encompass all of humanity, the Evils cannot be withstood or overcome by any one human or anything beholden to the laws of the Human Order; for just as Humanity is incapable of abandoning Wisdom, so too are the Evils an inevitable fixture of the Human Condition.

However, by the word of Gilgamesh in the 7th Singularity of Fate/Grand Order, the Evils of Man are the Calamities over which Humanity is destined to prevail.

Class Skills
Entities of the Beast class are stated to possess the following capabilities as Class Skills:

Independent Manifestation

 * Independent Manifestation (単独顕現) is a capacity which permits the unrestricted projection and materialization of the soul (魂の物質化) of the skillholder into a time period and location of his choosing. Being that the skillholder's soul fundamentally exists in a place beyond the boundaries of life and death and the limits of the History of Man, time travel may be enacted at will; and the projected flesh is in essence an immortal puppet controlled by the skillholder's consciousness. In the Final Singularity of Fate/Grand Order, Chloe von Einzbern implies that the Independent Manifestation exhibited by Goetia's Demon God Pillars (魔神柱) is comparable to the use of the Third Magic.
 * In the circumstance of Tiamat, Independent Manifestation is described as an expression the skillholder's existence across all eras and locales -- lending a general immunity against existential threats by way of time paradox or the conventional imposition of death (即死系攻撃).


 * Independent Manifestation is otherwise suggested to be a Class Skill shared among the Grand Servants by Goetia in the guise of Solomon the Wise at the end of the Fourth Singularity in Fate/Grand Order. However, it is unknown if his statements are indeed founded in fact.

The Authority of the Beast

 * The Authority of the Beast (獣の権能) is an Anti-Human skill that enhances the skillholder's capacity to harm existences that classify as Humans. In the specific case of Tiamat, it is stated that access to such a skill is held by right of standing as the Sea of Life (生命の海) itself -- being essentially a Divine Authority (権能) to destroy what one has birthed. It is likely that the skill as held by the other Evils of Man is justified by alternative means. Again by the example of Tiamat, the Authority of the Beast is apparently communicable to other entities per the will of the skillholder.

Self-Modification

 * To take the example of Tiamat, the skill of Self-Modification (自己改造) as held amongst the Evils of Man potentially permits the unrestricted fabrication and alteration of the skillholder's Saint Graph -- permitting, among other things, direct improvements to defense and other capabilities. This is achieved in Tiamat's case by way of freely reshaping the Black Mud (黒泥) of the Sea of Life (生命の海), which exists as an extension of her being. Per the circumstances of the Authority of the Beast, the mechanics and justification for the operation of the skill among the other Evils of Man likely differ from Tiamat's rendition.

Known Beasts
Aside from the Beasts that have so far made an appearance, Fate/Grand Order and Fate/Extra CCC mention the existence of several others:

Beast VI
Beast VI (ビーストVI) is stated within Tiamat's in-game profile to possess the Personal Skill known as Nega-Messiah (ネガ・メサイヤ) -- an ability of the same variety as Tiamat's Nega-Genesis (ネガ・ジェネシス), which generates a Conceptual Bounded Field (概念結界) that rejects the evolutionary course (進化) and the Genesis of the Earth (地球創世) expressed within the proper continuity of the History of Man (人類史), consequently proffering a resistance against the Noble Phantasms of any Servants generated as an output of the above processes.

Beast VII
In Chapter 14 of the Final Singularity, Gilgamesh states that as of the manifestation of Goetia, the Beast VII (ビーストVII) -- "the VII of the End" (終局のVII) or "the Beast That Announces the End" (終わりを告げる獣) -- will have appeared somewhere within the world. Additionally, in Chapter 4 of the Seventh Singularity, the Old Man of the Mountain mentions that, just as Pity (憐憫) is "one amongst the Evils" (悪の一つ), so too is Regret (慚愧).

Hakumen Konmou Kyuubi no Kitsune
In Fate/Extra CCC, the Hakumen Konmou Kyuubi no Kitsune (白面金毛九尾の狐) that speaks to Hakuno Kishinami within Tamamo-no-Mae's Secret Garden states that Tamamo is ultimately only an aspect of her; and that, in the manner that Divine Spirits are "merely extant" (ただそこにあるだけ) as temporal circumstances or phenomena (時勢、現象) fundamentally absent of human notions of positive or negative valence, so too is she "merely extant" as an Evil of Man. Furthermore, the expression of her existence and that of her aspects conform unfailingly to the present convictions of Man, much in the manner Divine Spirits; and thus, whether she manifests as benevolent or monstrous is inconstant, varying from era to era by the requirements of humanity.

As a Beast, the numerical designation associated with the Golden-Furred Fox unknown, and the Sin that she presides over is similarly unknown.

Primate Murder
In Chapter 15 of the Final Singularity of Fate/Grand Order, it is stated that the Primate Murder mentioned in the materials for Kagetsu Tohya is an alternate-world iteration of the Beast IV (ビーストIV), which is expressed within the continuity of Fate/Grand Order as Cath Palug (キャスパリーグ). However, as Cath Palug is more accurately a member of the Breed of Calamity (災害の種) -- the species that holds the potential to manifest the Beast IV -- it is unclear that Primate Murder is indeed a divergent expression of the same individual as the Cath Palug that appears before the Protagonist of Fate/Grand Order.

The Ancient "I"
In Melty Blood: Actress Again, the Dust of Osiris plots to crystallize the whole of the planet and its inhabitants as Philosopher's Stone (賢者の石) -- a medium by which to render the continuity of human history to permanent, imperishable record as a matter of preserving humanity against certain destruction. Arcueid Brunestud, upon learning of her plan, states that "the approach of overcoming death by reducing all things to zero" has been attempted before, and that the thinking behind it is a thousand years out of date -- having originally been the plan of the Ancient "I" (古い"一"). It is unclear if the Ancient "I" of the Melty Blood continuity is equivalent in meaning to Goetia's title as the "I" of the Original Sin (原罪の"一").