GC is a new concept for RPGs that was introduced with Lost Odyssey. GC stands for "Guard Condition" and in simple terms, is a wall between the characters on the front row and the characters on the back row. The higher your GC is, the less damage your characters on the back row will take. Your GC increases as the HP of your front row characters gets higher, for example if your front row was:
- Kaim: HP 2000
- Seth: HP 1500
- Tolten: HP 1300
Then your guard condition would be 4800. Once the wall has been destroyed by your enemies, your back row characters will take the same damage as those on the front row. There are also abilities and spells which can increase your GC number during a battle for example the skill Wall which can be Skill Linked from Mack, some enemies in the game can also use this ability. GC cannot be recovered by healing your allies HP.
There are ways to bypass your enemies GC to directly attack important enemies on their back row, For example, the Skill Break Hit which can be Skill Linked from Tolten. Sed's attacks also ignore GC, and at level 52, he learns Lucky GC Ignore which can be linked by immortals, giving them the ability to occasionally ignore GC as well.