Defeated enemy units drop a substance called Phantoma. The color of Phantoma indicates what aspect of the character it will replenish, though in general they automatically replenish a set amount of magic points. Phantoma are used in the game's leveling system, the Altocrystarium, to strengthen a character's magic skills. The game's magic skills are divided into five basic groups named after types of guns: for example, "Rifle" fires the spell in a straight line, while "Missile" homes in on and chases targeted enemies. Holding down the assigned action button increases the power of the attack. Many combat situations involve timed challenges. Success rewards the character, while failure drains their health. If a character is defeated in battle, the player can instantly select another to replace it, and the defeated character must be revived outside the mission. The game features an arena where practice fights take place. While these fights are not against real foes, the characters continue to level up and gain Phantoma after the battle, and twenty battles can be arranged at any one time. Each character has access to summoned monsters called which act as temporary playable characters and have their own set of skills. Summoning them empties the selected character's health gauge, removing them from battle until they are revived. Summons are also affected by the current environment: as an example, Shiva's powers are stronger in snowy weather. After a limited time in battle, the Eidolons are dismissed. Those available to players are series staples Shiva, Ifrit, Golem, Odin, Diablos and Bahamut. Each Eidolon has variants of its original form, many of which are unlocked as the game progresses.