In Tales of the Abyss, Additional Skills (アディショナルスキル Adishonarusukiru?), shortened to AD Skills (ＡＤスキル AD Sukiru?), are various passive skills that can add to a character's abilities and enhance gameplay. Most of these skills are unlocked through gaining stats with Capacity Cores. The required stat values for a given skill are based on the bonuses that are granted by the equipped C. Cores, which are added a character's base stat values upon each level up.