Xehanort's Guardian

Xehanort's Guardian is a Heartless-like symbiote used by Ansem, Seeker of Darkness throughout the Kingdom Hearts series, though it was first originally used by Xehanort. The Guardian serves not only to protect Xehanort from attacks, but also to fight for him when needed.

Kingdom Hearts Birth by Sleep
After losing to Aqua in the first half of their battle, Xehanort's great rage caused the Guardian to take shape behind him. After his second fight, Xehanort was struggling (with an internal struggle between Master Xehanort and Terra) within his heart used his Keyblade to stop the struggle with the Guardian dissolving and dragging Xehanort into the Realm of Darkness. Aqua then proceeded dive into the dark pool before her after him, sacrificing her armor and Keyblade to save Xehanort.

Kingdom Hearts
After conversing with Sora over the heart, Ansem, Seeker of Darkness proceeded to summon his Guardian, preparing to battle Sora due to his naïvity. It later appeared alongside him during Ansem's second battle with Sora, again transforming and increasing in size to become part of the World of Chaos. It, along with the rest of the World of Chaos, was destroyed at the hands of Sora.

Kingdom Hearts: Chain of Memories
In Kingdom Hearts: Chain of Memories, Ansem, Seeker of Darkness appeared in front of Riku in Castle Oblivion in an attempt to possess Riku as he had before. Enraged when Riku chose to fight rather than submit to him, Ansem again summoned the Guardian behind him. The Guardian attacking after Riku's transport to the abyss, its mighty fist barely missed him. The boy's final battle with the Seeker of Darkness then ensued.

Kingdom Hearts 358/2 Days
Realizing his loss to Roxas was inevitable, Riku transformed into a psuedo-Ansem, Seeker of Darkness and the Guardian to grab Roxas by the waist and squeeze him to the point of unconsciousness. This then allowed Riku to take Roxas to DiZ as assigned, the only downside being the fact that he was stuck in the form of Ansem, Seeker of Darkness.

Kingdom Hearts Birth by Sleep
The Guardian will fight for its master, grasping onto Aqua and carrying her high into the air, slamming her against the ground before returning to Xehanort. It may also send electrical surges forward from its fists. As it will do all in its power to prevent Aqua from attacking Xehanort, it may also perform a punching attack to drive her off. It may also fire dark energy balls before vanishing for a time and allowing Xehanort to land a few quick hits with his Keyblade. When the Guardian latches itself onto Aqua, the player must rapidly tap the button to escape a devastating attack. Dodge Roll can be used to avoid many of the Guardian's attacks. The Guardian will also be transported along with Xehanort and Aqua to a bright realm through Terra's remaining consciousness as it fights Xehanort from within. Here the Guardian will shoot an occasional energy ball. One can return Aqua to the real world by hitting Terra, or if they wait, activate a command unique to this battle. If the player correctly inputs the on-screen prompts, the battle will end instantly as Aqua and Terra double-team the Guardian and attack it with a burst of light. So long as the player heals when necessary and uses the proper Deck Commands, taking full advantage over Shoot Locks and Command Styles, both Xehanort and the Guardian should fall in due time.

Kingdom Hearts
The Guardian fights this time for Ansem, Seeker of Darkness. It will utilize the same tactics as past encounters, also able to fire disks of dark energy from its palms. When Ansem, Seeker of Darkness commands the Guardian to "come," it will temporarily defend him from all damage. When it latches onto Sora, a "?" will appear above his head. The Guardian will continue to attack Sora, changing the Attack option to Freeze. If Freeze isn't selected, it will drain a large portion of HP. When Xehanort's Heartless shouts "Take this!", the Guardian will create an energy shield before Ansem that damages Sora as Ansem flies into him. The Guardian also participates in one of Ansem's most powerful desperation attacks, rising up from the ground several times beneath Sora until the attack ends in a surge of dark energy.

When part of the World of Chaos, the Guardian does no damage to the player, merely creating strong gusts of wind to keep Sora away from Ansem.

Kingdom Hearts: Chain of Memories
The Guardian will perform the shock attack, punch tactic, and Ansem's most powerful desperation attack when fighting against Riku. It should be noted that in Kingdom Hearts Re: Chain of Memories, it also can fire the dark energy discs at the opponent.

Appearance
The Guardian has an ink-black muscular, humanoid form with its partially bandaged head with relatively human features, yellow eyes gleaming above a mouth filled with sharp teeth and two long antennae spouting from the top of the Guardian's head. A hole appears in-between more bandages on the torso in the shape of a heart.

While part of the World of Chaos, the Guardian mutates, its antennae becoming long horns, the rest of its body distorted by the darkness to look more muscular and ominous. Blue orbs rest on its shoulders, faint golden eyes also on the chest. Red and tendrils extend from the back, attatching to the Guardian with a snake head-like attachment. Its hands become massive wings, an extension similar to a scorpion's stinger juts out from its back. The torso also appears more skeletal.