Cerberus

Cerberus is a three-headed hellhound who guards the Underworld. He first appeared as Hades's loyal pet in Disney's , as guard dog to the Underworld. Cerberus serves as a boss in Kingdom Hearts, Kingdom Hearts II, and Kingdom Hearts coded.

Kingdom Hearts
Cerberus acts as a back-up plan for Hades if Cloud, who Hades promised to help in finding Sephiroth, fails his task of eliminating Hercules and Sora.

When Sora and Cloud's battle comes to an end (regardless of who wins), Hades sees that Cloud is no longer of any use to him, and sends Cerberus in. Cerberus quickly crushes Cloud beneath its front paw when his back is turned, and is about to attack the others, but is held off by Hercules, allowing Phil, Sora, Donald, and Goofy to escape.

Cerberus has Hercules, who is carrying Cloud, trapped, but Sora comes to help, returning the favor and allowing Hercules to escape. Sora manages to defeat Cerberus, and his efforts reward him the status of "Junior Heroes". However, as Sora leaves, Hercules mentions to Phil that he had already worn Cerberus down by the time Sora intervened.

Cerberus encounters Sora again in the Hades Cup, now more able to take more punishment, but the monster fails to defeat Sora.

Kingdom Hearts II
As Sora, Donald, Goofy, and Auron are escaping from the Underworld, Hades sends Cerberus to stop them. Donald and Goofy escape as Auron fights off the creature. Sora returns to aid him, but ends up separated from Donald and Goofy, leaving him and Auron to fight the monster by themselves. The two then manage to get away, and Cerberus is trapped behind the doors as they close, but not before Sora, Donald, and Goofy taunt him by making faces. Cerberus has its own cup in the Underworld, being the final opponent of the Cerberus Cup in a timed fight.

Kingdom Hearts coded
Data-Cerberus appears as a threat to Data-Hercules, Data-Cloud, and Data-Sora. He is one of four sources of the Bug Blox corruption in the Olympus Coliseum.

Appearance
Cerberus is a massive, three-headed dog with black fur and short, cropped ears. His heads are identical to each other, each sporting the same enormous mouths, pink tongues, and long, sharp teeth. All three heads also feature glowing red eyes. Cerberus's legs are rather short, and each ends in a paw with three grey claws. He also has a thin tail and seems to be quite muscular.

Personality
Cerberus has an angry and feisty personality, but will obey his master, Hades, whenever he is called into battle, as portrayed in Kingdom Hearts and Kingdom Hearts II. However, he will retaliate if Hades beats him too much.

Kingdom Hearts
It is important to be able to climb on top of Cerberus's back, in order to avoid his Dark Breath attack and his Fireballs. Alternatively, one may use Dodge Roll to avoid Cerberus's Dark Breath attack, or even deft running. Going under Cerberus when he uses Dark Breath will not work. Lock on to one of the outside heads and remain close to Cerberus's side.

Use the Guard ability to deflect his fireballs. Use his back and the stairs as places to heal, which is important to do often. Be sure to stock up on Ethers and Potions, or be sure to equip a Keyblade and items that give Sora at least 10 MP. Do not rely on Donald for healing, as he dies quickly, especially in the first battle.

Be sure to lock on and attack the heads on the side, not the middle head. Use Dodge Roll and/or Glide (or alternatively, Superglide) often to get away from his Bite. After several attempts to bite, he will stand on two legs and roar in the air. When he does this run away from him, or be ready to jump, as he is about to use a powerful shockwave.

Keep attacking the heads with your Keyblade and use a combination of Fire and Thunder magic to finish him off. While attacking the side heads, cast Aeroga on Sora to increase the damage. The reward for winning this battle is the Inferno Band.

Underworld
Cerberus is not an overly difficult enemy to defeat, he has just over two bars of HP. He is only fought once storyline wise, by Sora and Auron alone. The first thing Cerberus will (usually) do is jump right in front of Sora, so be ready to deliver an aerial combo. Auron's Bushido is immensely useful; although Sora should try to hit two heads with it.

The Star Seeker Keyblade is recommended, as its aerial boost will be helpful while performing aerial combos. Cerberus often swivels around leaving Sora nothing but his back, preventing damage. Just lock onto a head and start using combos, and Bushido whenever possible. If one wishes to use more magic, use Thunder on one head until Sora has almost no MP left, then use Bushido.

Use the Reaction Commands when caught between by the three heads to deal major damage. If Sora's HP gets low, stick to the edges and use Quick Run to avoid Cerberus when he jumps over to Sora. The Get Bonuses are an HP Boost for Auron, and Dodge Slash for Sora.

Cerberus and Cerberus Paradox Cups
The Cerberus and Cerberus Paradox Cups are timed battles, so one should be wary of the time constraint. Cerberus is fought alone, although Drives are available to use. Sora can use Valor Form for its quick hits, or play it safe and shoot magic bullets at Cerberus with Wisdom Form. Master Form is the most recommended form though, as all of the abilities Master Form has equipped will help Sora defeat Cerberus. Final Form is the best option (if available). Every single movement is an attack in itself, and this should buy time to keep on mashing. Do not compromise unless one has managed to take all the lesser enemies out within seconds.

Kingdom Hearts Re:coded
Cerberus in Kingdom Hearts Re:coded is quite a formidable opponent. His attacks deal good amount of damage, and he can attack Data-Sora, Hercules, and Cloud at the same time. Good timing of combos and blocking is crucial, and command decks should be filled by Cure commands so Data-Sora can quickly heal the party if the situation gets worse.

Using attack commands is not recommended as they deal insignificant amount of damage to Cerberus, so use normal attack combos. If having difficulty, Regen License is particularly useful, and Auto-Life License can be given to Data-Sora to make sure the battle doesn't end soon due to Data-Sora's defeat.

Origin
Cerberus originally appears in Roman and Greek mythology. He is depicted as a multi-headed dog (usually three heads) and acts as a gatekeeper of the Underworld, preventing dead souls that has crossed the river Styx from escaping. Cerberus is originally a three headed dog that Hercules had to battle in his trials in Greek Mythology and was a sibling to Chimaera and the Hydra.

In Disney's 1997 animated movie Hercules, Cerberus appears as Hades's "pet dog", and still has the same role as the gatekeeper of the Underworld.

Trivia

 * Although most of the world bosses in Kingdom Hearts Chain of Memories are the same as in Kingdom Hearts, Cerberus is replaced by Hades, who was an optional boss in Kingdom Hearts.