Ep 19. The Golden King

Shirou, Saber, and Rin are on the search for Archer, who has gone missing after his battle with Berserker. They decide to split up, with Rin investigating the Mage's Association and Shirou and Saber searching the city. Meanwhile, Archer has a conversation with Kuzuki Souichirou, the teacher at Ryuudou Temple, and Caster. It is revealed that Caster has been manipulating Kuzuki and intends to use him as a vessel in her ultimate plan.

As Shirou and Saber are searching, they come across a strange gate opening in the sky and a powerful aura emanating from it. They rush to investigate and find that it leads to Ryuudou Temple. There, they run into Caster and Kuzuki, who are in the middle of a battle with an unknown servant. The servant is revealed to be Gilgamesh, the Archer-class servant from the Fourth Holy Grail War.

Gilgamesh, also known as the King of Heroes, is one of the most powerful servants in the Holy Grail War. He is arrogant, ruthless, and believes himself to be superior to all other beings. He immediately attacks Saber and Shirou, but they are no match for him. Saber is defeated and Shirou is badly injured.

As Gilgamesh prepares to finish them off, Archer appears and an intense battle between the two Archers begins. Archer reveals that he is actually a future version of Shirou who has become disillusioned with his ideals of being a hero. He has decided to ally himself with Caster in order to prevent the Holy Grail War from happening and ultimately change history.

The battle between the two Archers is intense and each uses their Noble Phantasms, special abilities that are unique to each servant. Gilgamesh, however, proves to be too powerful and ultimately defeats Archer. Caster then reveals that she has been summoning the King of Heroes in order to use him as a pawn in her grand plan.

Saber awakens and the three heroes realize that they must work together in order to defeat Gilgamesh and Caster. They devise a plan to use their combined strength to destroy Caster's mana supply, rendering her powerless. The plan works, and Caster is defeated. Gilgamesh, however, is still a threat and continues to attack them.

Just as it seems like the trio is about to be defeated, Kuzuki reveals that he is actually a practitioner of a powerful martial art, empowered by Caster's magic. He attacks Gilgamesh and manages to destroy his armor, revealing his true form. The heroes take advantage of this moment and strike him with all their might, finally defeating the King of Heroes.

The episode ends with Rin, Shirou, and Saber realizing that their victory came at a high cost. They cannot allow themselves to become complacent, as there are sure to be more powerful enemies waiting for them in the future. They vow to continue fighting until they are the last ones standing and the Holy Grail is theirs.