Final Fantasy IX
Trance mode in Final Fantasy IX acts as a new form of Limit Break system that borrows heavily from Final Fantasy VII.
Unlike in Final Fantasy VI and Final Fantasy VIII, which were dependant on the percentage of HP a character had remaining, Final Fantasy IX's trance mode reverted back to a bar based system. The premise was once again much less ambiguous; once the character received enough damage, they would enter a state of trance.
Unlike in Final Fantasy VII, once the bar was completely full the character would enter a state of trance for an unspecified period of time. This meant that the moves could not be stored and once the timer limit was up, the character would revert back to a normal state.
No More Super Moves
With the exception of Zidane, all of the other characters have no specific moves which can only be performed while in a state of trance. All of the other characters have their natural abilities enhanced in some way that is relevant to their class type. This means that for example, Vivi can cast two black spells per turn instead of one and Steiner does 3x as much damage.
This did have its drawbacks though. Eiko and Vivi both depend on MP to reap the full benefits of their trance modes. This means that if they don't have enough MP, it is effectively useless. Zidane's special moves also require the usage of MP, but his normal melee attacks are enhanced too, so it isn't as much of an issue.
The majority of enhancements also become quite redunant due to the damage cap. Once Steiner does 9,999 damage with normal attacks, entering into a trance mode for 3x more damage doesn't actually achieve anything other than him changing colour.
Trance Kuja Shows It's Not Just About The Playables
What made the trance mode much more integral with the whole gaming experience in Final Fantasy IX was the fact that it wasn't just restricted to combat. Playable characters could be enveloped by it during parts of the story and this often led to them starting battles while already in trance mode, which gave a clear edge in combat.
However, what made it even more iconic was that it didn't just apply to characters which the player had control of. One of the more recognisable moments is when Kuja becomes Trance Kuja. His new-found trance mode enables him to reek havoc with immense destructive capabilities in one of the more memorable moments of Final Fantasy IX.