Crest Worms

Worms bound by Matou Zouken using a secret technique. They are his personal familiars. The worms are an extreme burden on the human body as they feed on their host and create artificial magic circuits within the host’s body. Anyone implanted with Crest Worms becomes Zouken’s puppet, physically incapable of defying him.

Fate/Zero Animation Guide I: Glossary of the holy grail war I