Seven Servants and three Pseudo-Servants appear in the animated special Fate/Grand Order x Himuro's World: Seven Most Powerful Great Figures Chapter. Aside from the Pseudo-Servants, they are all from the Fate/school life Servant creation contest.
Saber
Saber (セイバー, Seibā?) is the Saber-class Servant of Kane Himuro. Her True Name is Lê LợiWP (黎利, Rei Ri?).
In the story, she kills Berserker and fights Caster before being sent flying by Plato.
Archer
Archer (アーチャー, Āchā?) is the Archer-class Servant of Ayako Mitsuzuri. His True Name is Mehmed IIWP (メフメト2世, Mefumeto 2-sei?). There is another rendition of Mehmed II in Fate/Apocrypha.
In the story, he and his master observe Caster defeating Lancer.
Lancer
Lancer (ランサー, Ransā?) is the Lancer-class Servant of Issei Ryuudou. Her True Name is Lucky Mother (ラッキー・マザー, Rakkī Mazā?), the Mitochondrial EveWP (ミトコンドリア・イヴ, Mitokondoria Ibu?).
In the story, she fights Caster, evading her rockets in mid-air before being caught in a blast of flame along with her master.
Rider
Rider (ライダー, Raidā?) is the Rider-class Servant of Kaede Makidera. His True Name is DiogenesWP (ディオゲネス, Diogenesu?).
In the story, he and his master are incinerated mid-flight by Caster's flames.
Caster
Caster (キャスター, Kyasutā?) is the Caster-class Servant of Saeki Naomi. Her True Name is Leo IIIWP (レオ3世, Reo 3-sei?).
She carries a tubeWP which she uses to launch rockets, emit fire and for propulsive flight.
In the story, she defeats Lancer and Rider, and fights Saber before being sent flying by Plato.
Berserker
Berserker (バーサーカー, Bāsākā?) the Berserker-class Servant of Gai Gotou. His True Name is Nevil ShuteWP (ネビル・シュート, Nebiru Shūto?).
His body is that of a PanjandrumWP, with arms, legs and a mask-like face protruding from it.
In the story, he appears when his master confronts Kane Himuro outside the school, and while distracted by the sight of him being beaten up by her, he is killed by Saber.
Plato
PlatoWP (プラトン, Puraton?) is the Servant of Yukika Saegusa. His class is unknown.
In the story, he breaks up the fight between Saber and Caster at his master's request, sending both of them flying.
Pseudo-Servants
Assassin (Kaede Makidera)
Assassin (アサシン, Asashin?) is an Assassin-class Pseudo-Servant inhabiting the body of Kaede Makidera. Her True Name is Takuboku IshikawaWP (石川 啄木, Ishikawa Takuboku?).
Caster (Kane Himuro)
Caster (キャスター, Kyasutā?) is a Caster-class Pseudo-Servant inhabiting the body of Kane Himuro. Her True Name is Amelia Jenks BloomerWP (アメリア・ジュンクス・ブルーマー, Ameria Junkusu Burūmā?).
She is summoned after Kane had rejected the previous options presented to her by the Counter Force (Taro and JiroWP, LaikaWP, New NessieWP and Kajikawa YosobeiWP).
Friedrich Nietzsche (Yukika)
Friedrich NietzscheWP (フリードリヒ・ニーチェ?) appears as a Pseudo-Servant inhabiting the body of Yukika Saegusa.[1] Her class is unknown.
Trivia
So far, the servants shown in this special are the only canon version of servant that originally appeared in the 'Strongest servant'. However due to it being told by Yukika (Nietzche), both Gudao and Kane wonde if the story is true or not. making their appearance ambiguous at best.