Eraqus

Master Eraqus is a Keyblade Master featured in Kingdom Hearts Birth by Sleep. He is the master of Terra and Aqua, and he also serves as the second master of Ventus.

Kingdom Hearts Birth by Sleep
In the beginning of Kingdom Hearts Birth by Sleep, Master Eraqus prepares to hold the Mark of Mastery exam for Keyblade wielders and apprentices, while Ventus and Eraqus's long-time colleague, Master Xehanort, are present to witness Terra and Aqua endure their Exams. The exam is carried out soon afterwards, with Aqua passing while Terra fails, Eraqus believing that Terra is unqualified on the grounds that he is unable to control his darkness. Little does Eraqus know that Master Xehanort had used his dark powers to tamper with the course of the Exam itself.

Soon after, Master Xehanort goes missing. Eraqus sends Terra and Aqua to find him shortly after being contacted by Master Yen Sid about the spawning of the mysterious Unversed. Sensing a possible connection between the two events, Eraqus later instructs Aqua to look after Terra, as he fears his apprentice may be tempted by the darkness. However, after Terra departs, Aqua and Eraqus witness Ventus leaving as well, and he instructs Aqua to bring Ventus back.

As he reaches the end of his journey, Ventus discovers the truth about his past, and in order to get his questions answered, travels back to the Land of Departure so he may talk with Master Eraqus. Upon seeing Ventus he welcomes him back home with open arms but a confused and enraged Ventus was having none of it. When Ventus questions him about the χ-blade and his role in its creation, Eraqus recalls a long-ago discussion between himself and Master Xehanort over the Keyblade War which was believed to be fought over the very weapon. Eraqus disagreed with Master Xehanort's hypotheses which threatened the worlds and attempted to fight Master Xehanort over it. However his attempt was futile as Master Xehanort quickly took him down with the use of his dark powers which left Eraqus scarred.

Wanting to put Master Xehanort's plot to an end for good, he turned his attention to Ventus and prepared to strike. Meanwhile, Terra had received this news from Master Xehanort, him being tricked into thinking that the only way to save Ventus from his grim fate was to eliminate his master. Terra arrives just before Eraqus is about to vanquish Ventus, Eraqus sensing that Terra has indeed descended into darkness.

Greatly saddened by the fact that he must use force to eliminate two of his apprentices and even angered when Terra refuses his orders to stand down, Eraqus charges forward only for Ventus to be thrown into a portal to Destiny Islands by Terra, who goes on to fight Eraqus alone.

Terra wins the battle and leaves Eraqus wounded, but as both begin to show remorse for their actions (Terra for fighting his father figure and Eraqus for turning his Keyblade on Terra and Ventus in the first place), Eraqus is ambushed and finished off by Master Xehanort himself, and he fades out of existence before he can collapse into Terra's arms. He is later mentioned during the final battle between Terra and Master Xehanort, with Terra alluding to Eraqus as his father figure and primary motive for defeating Master Xehanort.

Some time after Terra's possession at Master Xehanort's hand, their hearts begin to converse with each other inside the new Xehanort's body, and as Master Xehanort openly wonders how Terra can still counter him, he realizes that it is because Eraqus has "set foot into" Terra's heart, meaning that in some form, Eraqus is still alive.

Appearance
Master Eraqus, like his student, Terra, bears a distinct Japanese influence in his choice of clothing. He wears a white, red lined haori that has a hood, along with slightly shorter than normal, light-colored hakama. Underneath his haori, he wears a navy blue shirt with a large white X pattern on the front. He also has jagged scars over his right eye and left cheek inflicted by Master Xehanort, much like the wounds Braig received from Terra.

Like his pupils, Eraqus wears pieces of armor, in his case gold and black armored boots and a dull blue-green section that covers his abdomen. This second piece of armor sports the same symbol worn by his students near the top. Eraqus's black hair is tied into a short, high topknot, with one bang falling off to the right side of his face. He also has a short, triangular and a mustache. Eraqus's Keyblade Armor greatly resembles armor, fitting in with his Japanese theme.

Master Eraqus physically resembles, the creator of the Final Fantasy series.

Personality
Master Eraqus is a strong Keyblade master, caring for Terra, Ventus, and Aqua as his own children. Stern and willing to instruct, one major goal he has in life appears to be preserving peace throughout the worlds, as he rashly attacks Ventus when Eraqus discovers that through his dark half, Vanitas, Ventus can create the χ-blade. Unlike Master Xehanort, Eraqus has a staunch aversion to darkness and believes that it must be destroyed at all costs, a view that he has endeavored to ingrain into his apprentices. In his final moments, he even becomes concerned that his actions against Ventus and Terra were due to some darkness having snuck into his heart.

Despite his sometimes cold actions toward his apprentices, he still cares deeply for them. He has Aqua follow Terra out of concern for the youth, gives a pained apology to Ventus before attempting to destroy the boy, and sheds a tear when he is forced to face off against Terra. Despite the strain between him and Xehanort, Eraqus attempts to forgive his erstwhile friend, even welcoming him to help preside over the Mark of Mastery exam despite their last meeting ending in violence. Following his apparent demise at Xehanort's hands, Eraqus's heart settles within Terra's body in order to help him counter Xehanort's possession and hopefully regain his body.

Abilities
Master Eraqus serves as a boss for Terra, after Terra prevents him from executing Ventus. During battle, Eraqus uses many quick lunging attacks, and is able to land many hits before the combo finisher. He also has several desperation attacks, each based on the light element.

Weapon
Master Eraqus wields a rather basic Keyblade named "Master Keeper", which is grey in coloration. It has the appearance of an old fashioned skeleton key, and the teeth are shaped like an "E". Its Keychain is the Mark of Mastery symbol. He summons his Keyblade in a fashion similar to Terra, shrouded in a series of golden blocks.

Trivia

 * Mark Hamill, Eraqus's English voice actor, was chosen specifically by Tetsuya Nomura for his role as Luke Skywalker in Star Wars and because Nomura himself is reportedly a huge Star Wars fan.
 * His name is an anagram of "Square", a reference to Square Enix, the developers of the Kingdom Hearts series. Tetsuya Nomura stated in the Birth by Sleep Ultimania that he had actually forgotten the basis of the name, and that the producer had to remind him that it was an anagram.