In Kingdom Hearts, the Stealth Sneak was attracted to the darkness in Clayton's heart, and used him as a puppet to help it defeat Sora, Donald, Goofy, and Tarzan. However, the heroes prevailed, resulting in the death of both Stealth Sneak and Clayton, as it toppled on to him and crushed him to death.
The Stealth Sneak is a bipedal lizard resembling a chameleon. It has a yellow body, with five short spikes along its back. It often stands hunched over, holding its arms out in front of it. Its entire upper body is covered in stripes of various shades of green and yellow, reminiscent of camouflage clothing. Its hands and feet have four toes each, two in front and two in back, with black claws. Its prehensile tail is curled up behind it in a spiral. It has a mouth lined by short, pointed teeth, a pink tongue that can extend to surprising lengths, and large yellow and orange eyes with small black pupils. It also has a large, yellow horn on the tip of its snout. Its Heartless emblem is on its chest. The standard Stealth Sneak bears a strong resemblance to a chameleon that Simba roared at in The Lion King just before the wildebeest stampede.
In Kingdom Hearts Final Mix, the Stealth Sneak's upper body becomes completely light green and is covered in intricate, black markings. The only other noticeable changes are that its horn becomes white and its underbody becomes tan.
Both halves of the Stealth Sneak's name reference its ability to become invisible. "Stealth" means "acting in secrecy", while "sneak" means "to hide".
Sora will be facing the Stealth Sneak with Clayton as its rider. It is best to focus on attacking the Heartless first, depleting its first HP meter to render it visible. The Stealth Sneak then acts similar to Sabor. Continuously attacking it and using Fire spells will do major damage. During the first part of the battle, Sora can also use Thunder spells to strike at both Clayton and the Stealth Sneak simultaneously. If Sora attacks the Stealth Sneak long enough, it will buck Clayton off of it.
It has two main attacks, a lunge and a "spell" of sorts. The lunge can be dodged by Dodge Roll. When visible, the attack can be seen by the stance it takes before lunging, but when invisible, the best way to "see it coming" is by locking on to it, since the stance involves it lowering the head, which is what Sora locks on to. So when the Lock-on ring suddenly lowers, dodge. Its other attack can be seen either way. Its hands start glowing and it will extend them, and when it brings them together, the attack launches. Simply time a jump with the movements of its arms.
After Clayton is thrown off, focus on him more. When Clayton is defeated, so will Stealth Sneak. The Stealth Sneak does not have to be defeated before Clayton, though doing so will grant extra experience.