The Blue Materia is an enemy from Crisis Core -Final Fantasy VII-. It appears in a group with other Materia.
Its high Vitality and Spirit make it hard to inflict massive damage. The Materia in the Cage of Binding have a seemingly guaranteed drop of a Phoenix Down if the player does not have a Phoenix Down in their inventory already. This makes them an unlimited source of Phoenix Downs, the other being the superboss, Minerva.
Materia means "matter" or "substance" in Latin. It also means "subject" or "matter" in Italian, Spanish, and Portuguese.