Light & Darkness (ライト＆ダーク, Raito & Dāku?, lit. "Light & Dark") is an ability that appears in Kingdom Hearts II Final Mix. It increases the user's chances of turning into Anti or Final Form when they attempt to enter a Drive Form while in battle.
In Kingdom Hearts II Final Mix, Light & Darkness is a support ability. So long as it is active, the standard Drive Form system is deactivated, and any attempt to enter a Drive Form will redirect to AntiForm, unless it would have normally redirected to Final Form. Once Final Form is unlocked for at-will activation, Final Form will only activate if it is actually selected from the menu, meaning that for all practical terms, the other four Forms are replaced with AntiForm. However, this effect only works in battle.
Learning Light & Darkness
Kingdom Hearts II Final Mix