Lexaeus

Lexaeus, the Silent Hero, is number V in Organization XIII and one of its founding members. He appeared in Kingdom Hearts:Chain of Memories during Riku's storyline, working with Zexion and Vexen to try and manipulate Riku into serving them. Lexaeus wields a large tomahawk in battle, using his enormous strength and the power of Earth to combat his opponents.

In Castle Oblivion
Organization XIII first appeared in the series during the events of Kingdom Hearts:Chain of Memories in Sora's storyline. Much of the Organization members' activities centered around the rivalry and strife within the Organization. Lexaeus was heavily involved in this feud, which originated from spite between senior members of the Organization and younger members like Marluxia and Larxene.

When Larxene and Marluxia began to show signs of dissent, Zexion and Lexaeus began monitoring the castle and their activities. Also active in the castle were Axel and Vexen, two other members of the Organization. Axel was too unpredictable to trust, but Lexaeus and Zexion enlisted Vexen's help in spying on Marluxia. After learning that Marluxia planned to make use of Sora's power by deceiving him into feeling loyalty to Naminé, they decided to make similar use of Riku.

Confronting Riku
Vexen tried to make use of Riku's power by gathering data on him and creating a replica, but his experiments were interrupted. Though he succeeded in creating the replica, he was killed my Axel on Marluxia's orders before he could achieve total control over it, and the replica became independent, searching for a heart.

Shortly before Sora confronted Axel and Marluxia at the top floor of Castle Oblivion, Lexaeus appeared before Riku, trying to sway him to give in to the darkness inside him and use his full dark powers. Riku refused to cooperate, and Lexaeus attacked him, hoping to destroy him if he could not be manipulated. Despite his incredible strength, Lexaeus was defeated, and with his last breaths, enveloped in the darkness present in his heart. Although his ploy had an effect on Riku, Riku was able to overcome it and continue on his journey.

Lexaeus in Battle
Lexaeus is exceptionally strong physically, and uses the element of earth to reinforce his attacks. He regularly strikes at Riku using his enormous tomahawk, and can hurl it into the air only to have it come down and flail about the combat area. Like several other Organization members, Lexaeus has the ability to levitate, which is the only magical abilities he displays. He does have some other supernatural abilities, however; Lexaeus can dig out chunks of rock form the floor and heave them at Riku, and can also strike the floor with such force that it tilts.

Links
Video of cutscenes before and after battle with Lexaeus

Video
e5TFFfdLUSw