Drive Forms are an ability originating in Kingdom Hearts II and are introduced in The Interference (story).
Drive Forms are a combat ability that take advantage of the co-operation of party members. They spend a unique power reserve called the Drive Gauge, which refills only with the defeat of enemies, thus severely restricting their usage.
When the Drive Form activates, one or more Party Members are absorbed into the user's body. The user's set of abilities are replaced with a much more powerful set. Using a Drive Form can restore all HP and MP, making it incredibly useful in a pinch.
Drive Forms are accompanied by specific symbols and colours. When using the Drive Form, the user's clothing is decorated with those colours. Also, each Drive Form is associated with a specific ability, which can be used outside of the Form once enough experience with the Form is gained.
Valour Form is a form with the colour red and the fleur-de-lis as its symbols. In Kingdom Hearts II it is performed specifically with the aid of Goofy.
It is characterised by an increase in physical strength and speed and a lack of ability to cast magic. Its special ability is High Jump, which allows the user to jump twice their regular jump height.
Wisdom Form is a form with the colour blue and a blue flame pattern as its symbols. In Kingdom Hearts II it is performed specifically with the aid of Donald.
It is characterized by its inability to commit direct attacks; instead the user glides across the floor, firing energy shots from their equipped weapon. Its special ability is Quick Run, which allows the user to dash in short bursts.
Master Form is a form with the colour yellow and a grey cross as its symbols. It uses two party members.
In terms of abilities, it is a fair balance of physical and magical attacks. It is characterized by its aerial fighting style, with the user jumping into the air with every attack. Its special ability is Aerial Dodge, which enables the user to 'jump' a second time in mid-air.
Final Form is a form with the colours white and silver and a white swirl as its symbol. Though from an external perspective it uses two party members, it technically uses three, as Final Form can only be activated with the aid of Sora and Alex's counterparts.
Final Form allows its user to float above the ground, and jump much higher than normal. The user's weapons are controlled via apparent telekinesis and will protect the user during the slightest motion. Its special ability is Glide, which enables the user to glide through the air instead of simply falling.
Anti Form (parsed in Kingdom Hearts II as 'AntiForm') is a form with the colour black and blue swirls as its symbols. Anti Form is not really a standard form - it is explained as a "a glitch in the process". Unlike each of the other forms, Anti Form does not have to be triggered by will, and has the ability to hijack the use of any other form. In Sora, it is a sort of flashback to a time when he was a Shadow Heartless; in Alex, it is a reaction to his heart's composition mostly being that of darkness.
Anti Form is characterized by the user's appearance, gait and attacks becoming very similar to that of a Shadow Heartless, with an entirely black appearance, yellow orb eyes and wisps of darkness. Any equipped weapon disappears, leaving the user with only the ability to scratch and kick at enemies. Anti Form is fast, but it is also weak, and is incapable of using any items or magic, meaning it is incapable of healing from damage.
The only way to obtain the power of Drive Forms is to own clothing created and enchanted by the Three Good Fairies, Flora, Fauna and Merryweather. This unlocks the power of Drive Forms by standard, but further Drive Forms must be either granted or realized.
Because Drive Forms are innate to certain objects rather than a skill acquirable through birth or practice, there are only two people known to be able to employ Drive Forms.
As per Kingdom Hearts II canon, Sora acquires his Drive Forms after getting his old, undersized adventuring clothes reworked into new ones. He initially gains Valour Form from the fairies, and Wisdom Form after the adventure in Timeless River. Both Alex and Sora gain Master Form from King Mickey. Sora is the first of the two to be able to use Final Form, though its traditional trigger - fighting with Roxas - happens much earlier than it should have done.
Sora has only entered Anti Form once, but it resulted in his defeat by Xaldin.
Due to the misbalance of Alex's heart, Alex initially has the ability and tendency to activate Anti Form on purpose, though it has a much more noticeable effect on his sanity than it does on Sora's. Eventually, Alex does not require his enchanted clothes to use Anti Form.
- Kingdom Hearts II, 2005