The Green Materia is an enemy from Crisis Core -Final Fantasy VII-. It usually appears a group with another Materia.
Its high Vitality and Spirit ratings make it hard for Zack to inflict massive damage. Use strong Command Materia such Assault Twister+ or Costly Punch.
The Materia in the Cage of Binding have a seemingly guaranteed drop of a Phoenix Down if, and only if, the player does not have any Phoenix Downs in their inventory already. This makes them the one of only two unlimited sources of Phoenix Downs in the game, the other one being the superboss, Minerva.
Materia means "matter" or "substance" in Latin. It also means "subject" in Italian and Spanish, and is the ascendant of Portuguese "Matéria".