Air Blade is an airbending ability that creates a spinning blade and shoots it where you are looking. It is one of the only moves that causes direct damage for airbenders. The damage can be increased every time you hit an enemy.
As with all other abilities, there are two choices for Air Blade's level IV upgrade.
Chainblade: Bounces through enemies
This upgrade makes the blade bounce between nearby enemies. It's good against a group of enemies because it deals damage to all of them.
Chainsaw: Cuts through blocks like stone
Chainsaw allows the air blade to go through blocks of hardness 2. This means that this upgrade adds an utility factor to this ability. It can also hit enemies that are hiding behind blocks but the airblade will disappear upon hitting an entity.