The Rock Titan is an enemy from Kingdom Hearts and Kingdom Hearts Re:coded. The Rock Titan makes a cameo appearance in Kingdom Hearts II during the opening cinematic for the Olympus Coliseum. However, he isn't credited in Jiminy's Journal. It originally appeared in the animated film Hercules, under the name Lythos. He is the final fight in the Hades Cup in Kingdom Hearts, and inhabits Layer 15 of Olympus Coliseum as one of the four sources of bugs in Kingdom Hearts Re:coded.
The Rock Titan is a gigantic, bulky creature that seems to be composed entirely of rough, uneven stone. Its body is very large and barrel-shaped. Its legs are short and its feet are flat, while its arms are relatively long and end in four-fingered hands. It has two comparatively small, draconian heads placed side-by-side on the top of its body. Both heads have thick necks, a peculiar lower jaw with four very large, blunt teeth. Its eyes are very small and red, and the inside of both mouths are red as well.
The Rock Titan's name references its stony body, while "titan" is derived from the Titans of Greek mythology, which were loosely represented by the Rock Titan and its companions in Hercules.
Lock on to one of the Rock Titan's big feet and attack it with combos (such as Ars Arcanum and Graviga). When the Rock Titan falls on its back, use the Superglide ability to float to one of the heads and attack from the far side. Be careful though, as the heads will swing at you; Dodge Roll/jump to avoid damage. Beware of the shock waves it releases, a single foot-stomp can deplete more than half of Sora's HP. The suggested magic spells to use in this battle are: Curaga and Aeroga.
However, a somewhat faster plan is to equip a powerful Keyblade (such as Lionheart, Oblivion, or Ultima Weapon), and repeatedly hammer the legs with Arcanum or Sonic Blade until it falls down. Then, just keep using Arcanum on the heads, as it will deal a large amount of damage. Using this method, the only magic you really need is Curaga. However, if you use Aero, it will take damage simply by you being near it.
Note that each hit taken by the Rock Titan gives you 1 Tech Point, thus you have an option of returning to the battle with the Rock Titan to level up quickly.
The Rock Titan has few attacks, they are also not used very often. The first one consists of a ground attack in which he lifts his hands and pounds the ground releasing a large shockwave that can be easily evaded by jumping. The second attack, similar to the first, consists in the Titan lifting one of his feet and stomping it down. The last (and most powerful) attack appears when he's knocked on the ground and Sora gets the chance to attack his heads; with biting similar to Cerberus' the Titan tries to keep Sora's attacks at bay.
The Rock Titan first appeared in Hercules as part of Hades' evil plot. When the planets align, it is the opportune time to summon the titans, supposedly. With Hercules' power, Hades destroys the prison in the ocean where the Rock Titan and company was and the titan climbs out of the ocean wreaking havoc on Greece. The titans head for Mount Olympus, where they attempt to get rid of Zeus. Hercules later comes to the rescue by using the Wind Titan to suck the titans up and send them flying into space putting an end to the Rock Titan.
 See also