Once you have accepted the quest Wisdom's Echo, make your way through Aveclyff until you reach the very bottom of the Lower Central Region. There are 20 Landworm groups here, easily linked by Timeshift, that are instantly respawnable. Each group of 20 Landworms yields 99 enemies - or +99 on Battle Chain. After 370 chains you earn twice as much EXP, and only leaving for the world map or completing the quest will break the chain. Hence, you gain a massive amount of Stats increases, new Arts, and Art upgrades by defeating very easy enemies over and over.