Actions with Triggers

You can use free actions that have triggers and reactions only in response to certain events. Each such reaction and free action lists the trigger that must happen for you to perform it. When its trigger is satisfied—and only when it's satisfied—you can use the reaction or free action, though you don't have to use the action if you don't want to. There are only a few basic reactions and free actions that all characters can use. You're more likely to gain actions with triggers from your class, feats, and magic items.