Also known as: 刻印虫
Insects seen in the Fate series, which incubate in their host and grant them the ability to use magic at the cost of shortening their lifespan. Appeared extremely phallic in the original release of Fate/Stay Night, but was edited for the Realta Nua release and anime adaptations.
Matou Kariya uses an evolved form of the crest worms, blade wing worms, in combat.