It has fast movement speed, high health, high damage output, decent range, hits multiple cats, and can do a Critical Hit sometimes. All in all, a devastating enemy. First form Bahamut Cat might be able to help in earlier stages if you do not have ranged decently-leveled attackers such as Dragon Cat or Crazed Dragon Cat.
Awakened Bahamut Cat can be used to chip off much of a 100% buffed R. Ost, then let it be finished with the rest of your attackers.
Dark Mitama can easily perma-slow this avian atrocity from long distance, rendering it powerless.
Dragon cat, Macho legs cat, Manics macho legs cat and manic king dragon will do fine against R.ost
Stressed about recent hair loss. Yes, his last name is actually Ost. His first name is Rich. Can critical sometimes.
Recently, hair loss began to worry
Ostrich club. By the way in until the ostrich is the same last name, good meeting is the name. Sometimes it unleashes critical.
A Metal enemy that only appears in the Golden Week and Silver Week events. It drops less money and has the usual Metal ability of only taking 1 damage except for Critical Hits, but it has much lower stats all across the board and cannot perform Critical Hits itself.