For a long time, I always interrupted your conversations, but from now on I'm sure that I can only squeal. Never mind, for it's like a normal day for you guys. Yet, it does sounds lonely. So in the end, I only want to say goodbye to you.
~ Fou's last words before he lost his sapience and reduced into a mindless animal (temporarily)

Primate Murder, also known as Fou, Cath Palug, Fourth Beast and the Beast IV, is a minor but pivotal antagonist in Tsukihime (mentioned as one of the 27 Dead Apostle Ancestors) and one of the main characters in Fate/Grand Order.

In the latter version, where he took the identity as Fou, a creature petted by Merlin, he becomes a supporting antagonist in the Final Singular after being revealed to be one of the Evils of Humanity. He is also the pet of Merlin, whom Fou shared a physical resemblance with and strongly hated. He is ultimately defeated in a roundabout way at the end of Observer at Timeless Temple.

He is voiced by Ayako Kawasumi in Japanese version (who is known for voiced all alternate versions of Saber/Altria Pendragon including Saber Alter) and by Abby Trott in English version of - First Order - anime.


Taking the idenity as Fou, the Beast IV seemed to be an animal that appears to be able to freely walk around the Chaldea Security Organization's complex and has a notable attachment to Mash. The protagonist meets it alongside Mash, and it then tends to come along on the various Singularity missions.

He is in actuality a Cath Palug who belongs to Merlin and in other universes where the Human Order was weaker, would've belonged to Altrouge Brunestud, the ninth of the 27 Dead Apostle Ancestors as the Primate Murder, the first of the Dead Apostle Ancestors and ultimate killer of humanity. It is the Fourth Beast and represents the evil of Comparison (as in envying stronger people and regretting for one's own weakness).

By the end of Observer on Timeless Table, initially becoming an enemy after his identity's expose, Fou eventually redeemed himself and sacrificed his own sentience, to revive Mash in a last ditch of helping the Protagonist into fighting Goetia. After the event, Fou was reduced into merely a mindless animal.

However, during Cosmos of the Lostbelt, Fou shows that he regained sentience during the chapter of Norse Mythology. In later events, he even managed to have dialogues that could be translated into human language, indicating that he fully recovered his understanding over humanity. Fou is also shown to be in good terms with Ophelia Phamrsolone, as he hugged her according to her request before the final showdown against Surtur. By the time Chaldea arrives at the Wandering Sea, Sion notes that he has some sort of sapience and is still growing.


  • In Tsukihime, the White Beast is merely mentioned as being the first of the 27 Dead Apostle Ancestors with very minimal info on what the beast even is.
  • Fou/Primate Murder is so far the only Beast that has no boss battle after its introduction.
  • Strictly speaking, Fou isn't the true Primate Murder in Tsukihime, but instead an alternate possibility for what the White Beast could have become. Whereas Primate Murder grew into a savage animal specializing in killing humanity, Fou is a cute critter who watches over mankind's fight and eventually gives up his sapience to save a human being. Fou still had the potential to become Primate Murder, but needed a different perspective and a few more centuries to gather power.


           Flg.webp.jpg Villains



Assassin | Beast of Revelation | Caster

Masters & Humans

Manaka Sajyou | Sancraid Phahn | Misaya Reiroukan

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Masters & Humans

Kirei Kotomine | Kiritsugu Emiya | Ryuunosuke Uryuu | Byakuya Matou | Kayneth El-Melloi Archibald | Sola-Ui Nuada-Re Sophia-Ri


True Assassin | Assassin | Caster | Saber Alter

Black Shadow

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Masters & Humans

Zouken Matou | Dark Sakura | Kirei Kotomine | Shinji Matou | Souichirou Kuzuki | Illyasviel von Einzbern


Gilgamesh | Archer (Unlimited Blade Works) | Assassin | Caster

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Dr. Heartless | Faker | Gilgamesh | Kayneth El-Melloi Archibald | Sola-Ui Nuada-Re Sophia-Ri | Ernest Fargo | Gurdoa Davenant | Trevor Pelham Codrington | Marisbury Animusphere

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False Masters
Jester Karture

False Servants
False Archer | False Berserker

True Masters
Faldeus Dioland | Francesca | Bazdilot Cordelion | Sigma

True Servants
True Caster | Watcher

Filia | Master of Archer | Cashura | Kuruokas | Wolf's Creator

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Twice H. Pieceman | Leonardo Bistario Harwey

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Kiara Sessyoin | BB | Kazurodrop | Kirei Kotomine | Shinji Matou

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Souren Araya | Kirie Fujou | Fujino Asagami | Cornelius Alba | Misaya Ouji | Satsuki Kurogiri | Lio Shirazumi | Meruka Kuramitsu

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Yggdmillenia Clan & Black Faction

Darnic Prestone Yggdmillenia | Celenike Icecolle Yggdmillennia | Assassin of Black | Caster of Black | Lancer of Black

Red Faction

Shirou Kotomine | Archer of Red | Assassin of Red

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Beasts of Calamity

Goetia | Tiamat | Kiara Sessyoin | Mara | Primate Murder | Koyanskaya | Beast of Revelation | VII of the End

Part 1: Observer on Timeless Temple

Heroic Spirits

Jeanne Alter | Jason | Goddess Rhongomyniad | Mephistopheles | Gorgon | Kingu

Allies of the Beasts

King Solomon | Lev Lainur Flauros | Demon Pillars | Laḫmu


Zolgen Makiri | Marisbury Animusphere

Part 1.5: Epic on the Remnants

Demon Pillars


Phantom Demon Alliance (Archer of Shinjuku | Avenger of Shinjuku | Archer Alter | Assassin of Shinjuku)


Rider of Resistance | Caster of the Nightless City


Kiara Sessyoin


Caster Limbo



Part 2: Cosmos of the Lostbelt

Kadoc Zemlupus | Ophelia Phamrsolone | Hinako Akuta | Scandinavia Peperoncino | Kirschtaria Wodime | Beryl Gut | Daybit Sem Void

Lostbelt Kings
Ivan the Terrible | Skadi | Qin Shi Huang | Arjuna Alter | Zeus

Alien God's Force
Alien God | Priestess of the Alien Star | Koyanskaya | Emissaries (Kirei Kotomine | Caster Limbo | Senji Muramasa)

Crypters' Servants
Anastasia Romanova | Sigurd | Prince of Lanling | Xiang Yu | Ashwatthama | Dioscuri Twins | Caenis | Grand Berserker

Lostbelt Inhabitants
Oprichniki | Surtr | Qin Liangyu | Odysseus | Lostbelt Olympians

Archer of Red | Caster of Black | Kama | Goetia

Event Villains

BB | Black Grail | First Lady | Testement | Ultra Heroine Z | Zouken Matou | The Master With No Name | Darnic Prestone Yggdmillenia | Kama | Space Ishtar | Xu Fu | Serizawa Kamo

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