
During an interview with Square at E3, the summoning system for Final Fantasy XIII was discussed.
Each character has one, and only one, summon tied to them. Characters will work with this specific summon during battle, actually interacting with them as opposed to just triggering a spell effect. This new system will take the place of Limit Breaks from past Final Fantasy titles and is being labeled the "gestalt" system (gestalt meaning a sense of wholeness).
Watch the Full interview below.
Source: GameTrailers