In previous Dragon Quest games, there were skills that can increase damage on the next attack, like Psyche Up and Charge Up.
What is Tension?
Tension is a state of building up power to unleash in a future action. In Dragon Quest VIII, every party member has an option called Psyche Up found at the bottom right of the battle options. This allows the player to take a turn to build up tension. The more times tension is built, the more powerful the next action will be. There are four levels of tension, representing percentages that the next action will be: 5, 20, 50, and 100. These percentages are added to the normal stats of a character.
It also works on magic: offensive, defensive, and healing as well.
Angelo's Multiheal spell will heal ~100 HP to everyone. In a state of 50 tension, it can heal ~150 HP to everyone.
Tension does not work on skills that do no damage nor is it depleted when using such skills, such as the Underpants Dance.
Once an action like attacking or spell casting uses tension, tension is returned to the normal level.
Some enemies also have the ability of building tension, making them tougher in battles.
Super High Tension
Using Psyche Up normally, a party member can reach 50 tension without difficulty. However, there is a chance that a party member will not reach 100 tension, causing the action to fail. However, that party member doesn't lose the tension already built. When a character reaches 100 tension, their sprite animation may change and they can inflict extreme damage on enemies.
Other Ways of Building Tension
Besides Psyche Up, there are other ways of building Tension. In Dragon Quest VIII, the Timbre of Tension boosted everyone's tension levels by one. A player could make High Strung Cheese, boosting everyone's tension levels by one. In Dragon Quest IX, the Hero has the ability Egg On, building another party member's tension level by one.
There are limits to Tension. Tension does not carry over from battle. A player loses tension if they are put to sleep, paralyzed, cursed, hit with War Cry, or defeated in battle.