Everything was peaceful until it attacked it wasn't a person or nation rather a virus that strips people of their bending only few people are left that can still bend yet they blame it all on one person kirasi a water/fire bender her ,her friends and a few others are the last people well not the last who can still bend the nations are counting on the avatar , are counting on her to restore balance and peace but like they said being the avatar isn't easy but being azula's descendant isn't easy either .