For those who have not completed Xenoblade Chronicles, this page or section may contain spoilers regarding the plot. Discretion is advised.
When a physical attack is blocked in Xenoblade Chronicles, the damage dealt by the attack is reduced by 50%. A target can block attacks even if attacked from behind.
Block Rate is the probability of blocking an enemy's attack, and is determined by the level difference between the party member and the enemy, plus bonuses received from skills or other sources. Both physical Arts and auto-attacks can be blocked. Ether Arts cannot be blocked.
Enemies are also able to block party member's attacks. If an enemy blocks an attack, the party member will lose tension.
Blocked attacks cannot Topple opponents.
If an attack is blocked, the attacker will refrain from movements or attack for a short period (approximately 0.5 - 1.0 seconds). The defender will also be stuck in animation. This can be bad for Reyn and Dunban who get much aggro from many sources. If they have high guard, they can be stuck in blocking animation for quite a while before they can auto-attack or use arts.
Some characters and enemies have attacks which can hit two or more times with each attack. If one of the hits is blocked, the remainder of the attack is cancelled.