At the beginning of the first round of combat, all participants make an Initiative roll: d20 + Dexterity Modifier + Feats. A character's Initiative roll determines when they act during a combat round. Characters who roll higher will cast spells, activate abilities and attack faster than other characters with a lower Initiative score. In addition, a character with a higher Initiative score will treat slower opponents as Flat-Footed, denying them Dodge and Dexterity bonuses to Armor Class and allowing them to perform Sneak Attacks. While almost exclusively a function of your Dexterity Modifier, you can also significantly improve your Initiative with the Improved Initiative feat.