The Crystarium is a character's growth chart, with which you can buy various upgrade nodes:
- **Ability** node teaches character a new ability.
- **HP** node increases character's maximum HP.
- **Strength** node increases character's Strength stat.
- **Magic** node increases character's Magic stat.
- **Accessory** node increases character's accessory slots by 1.
- **ATB** node increases number of segments in chraracter's ATB gauge by 1.
- **Role** node raises character's role level by 1.
See the Crystarium section of the guide for a detailed look at an optimal progression through the game for each character.