An Berserker-class Servant from Third Singularity, Okeanos. He lives on a remote island where Francis Drake arrived in search of treasure.
While exploring the island where Drake's ship is stuck, Ritsuka and his group find themselves in a cave similar to the labyrinth of Crete. Lost in it, they meet and engage in a fight with Berserker, but soon they are interrupted by Euryale. She explains that Asterios, Berserker's True Name, is protecting her from another pirate. Drake offers her protection in exchange for help, and Euryale and Asterios join her team.
