Grail-kun has no discernible origin in the Carnival Phantasm world.
Grail-kun is a mascot-styled version of the Great Grail.
Styled after Doraemon, Grail-kun listens to the worries of his friends, tells them they are hopeless, and gives them a tool to help them obtain their desires.
Grail-kun appears in three segments featuring characters coming to him for help. The first involves Shinji Matou seeking help to have Gilgamesh listen to him, becoming shocked upon receiving the "Friendmaker." The second involves Shirou Emiya saddened that Archer says he'll never become a Hero of Justice, becoming shocked upon receiving the "Hero Creation Kit." The third features Kirei Kotomine complaining that Lancer is useless because of his constant deaths, quickly agreeing with the use of the "Servant Strengthening Device."
Grail-kun appears to Lancer in the "Final Dead Lancer" episode, telling him how to avert his deaths. He says Lancer is the clown of the festival and that the story will kill him. As Lancer avoids his deaths, Grail-kun is shown various times, eventually revealing that Lancer ultimately needs the Grail to avoid death. After Lancer is killed, Grail-kun chides him for not avoiding them all.
Fate/Zero Please! Einzbern Consultation Room Edit
Grail-kun makes a cameo in the last episode as a pattern on Eri's knitting.
Fate/kaleid liner PRISMA☆ILLYAEdit
Grail-kun appears as a toy prize at a festival.
Grail-kun gives out a variety of tools to help others. He can appear and disappear at will.
« Go show him who's boss. »
The Friendmaker (ナカヨクナール, Nakayokunāru?) is given to Shinji to help Gilgamesh obey him.
Hero Creation KitEdit
« You'll be a hero after killing a million people. »
The Hero Creation Kit (英雄製造キット, Eiyū Seizō Kitto?) is given to Shirou to help him become a Hero of Justice.
Servant Strengthening DeviceEdit
« You should just kill him and forge a contract with another Servant. »
The Servant Strengthening Device (サーヴァント強化装置, Sāvanto Kyōka Sōchi?) is given to Kirei to make Lancer useful. It is the only one of Grail-kun's tools put to use.