Antiform

Antiform is a Drive Form which appears in Kingdom Hearts II. It uses both party members, and consumes all of Sora's Drive Bars. It represents the darkness that still dwells within Sora's heart, and is obtained along with Sora's new clothes at Mysterious Tower. Its emblem is a black demonic silhouette.

Mechanics
Unlike other Drive Forms, Antiform cannot be purposefully activated. Instead, it will be randomly activated when Sora attempts to enter Valor, Wisdom, or Master Form, based on a hidden "Anti Point" counter. This counter is increased by 1 every time Valor, Wisdom, or Master Form is activated, but is reduced by 10 when Final Form is used. Gameplay-wise, the Antiform exists as a consequence of abusing the Drive system, and is meant to be "strong but troublesome". However, the counter system is ignored while the Two Become One Keyblade is equipped, as its Light & Dark ability will make it so only Antiform or Final Form activate when Form is used. Antiform starts at having a 75% chance of being the activated form when Form is used in this state, but goes down to 50% and then 0%, until Final Form is obtained. It is also impossible for Sora to enter Antiform while an unconscious ally is on the field, or if he was trying to change to Final Form. Antiform can only be manually deactivated outside of battle, though its Drive Gauge caps out at 6, and consuming Drive Orbs will actually cause the gauge to be consumed faster. In addition, though Drive Forms normally persist through cutscenes and Cup seeds, Antiform will instead revert to Standard Form.

Unlike the other Growth Abilities, Antiform's "Anti Glide" ability cannot be leveled and is thus inaccessible in Standard Form. Like Valor Form, Antiform cannot use magic; in fact, it cannot use any commands beyond "Attack" and "Return to normal". Furthermore, Sora cannot pick up HP Balls while in Antiform, meaning he is completely unable to heal in any way. Although Sora moves at twice his normal speed while in Antiform, he takes 50% more damage from attacks, and doesn't gain experience from defeated enemies.

Strategy
When using Antiform, the lack of any method of healing means that the player's main goal will be to evade the enemies. Although Antiform's high speed and Anti Glide ability make it easy to stay safe through simply evading the enemy's attacks, its quick combos will often let it keep an enemy stunned while also dealing damage, and can also deflect many attacks automatically. Furthermore, several of Antiform's attacks have a neutral or dark attribute, allowing them to break through enemies which are immune to the weapon-attribute, like the Large Body.