The story blends the Celtic belief in King Arthur and the Holy Grail with Christian stories of the Eucharist. This extends the ideology of "pure blood," as the Holy Grail is said to have been the cup that caught the blood that fell from Jesus' side when a Roman soldier pierced him. The quest to find the Holy Grail is also used to justify the Crusades and the increase in anti-Jewish massacres, as Jewish people are perceived as having "impure blood."