is the second stage in Sub-chapter 25, Scars of War
Starts off with some Hyppoh and other peons. After you attack the base, Master A and 2 Chickful A's are spawned. He has a high strength magnification, so beware!
Dark Emperor Catdam can help a lot, if you stack him at the beginning. Dragons can deal with the Chickful A's. Crazed Gross has a somewhat helpful shockwave.
You can also try using bulky cats like jamiera to land a hit on master A. Or if you have him,awakened bahamut.