In Xenoblade Chronicles for the Wii, a character’s tension is shown as the bar beneath their portrait. When the bar fills up, they’ll go “on fire” and be pumped up for battle.
Tension has several effects, but primarily it raises the chance to hit successfully. A low tension will make them miss a lot.
Tension also plays a large part in performing chain attacks. Having all of your characters with max tension will give you a higher chance to perform longer chain attacks, doing much more damage.
Tension is raised in several ways. Successful hits, winning battles, and cheering on your teammates are sure fire ways to increase tension. Keep an eye out for those quick time events during battles, and press the B button at just the right time to get a tension boost.
A sure fire way to put the entire party’s tension bar to the max is by changing the future. Sometimes during battle, you’ll see a vision bar pop up warning you of an enemies next move. If you can manage to kill an enemy while that vision bar is visible, you’ll break the vision bar and change the future, which raises all tension bars to the max.