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
''One of the true Keyblade Masters and also Terra, Aqua and Ventus's teacher. He has a strong aversion to darkness, and believes it the duty of every Keyblade Master to rid the world of it.''

Though strict on the outside, he is not unkind, and loves his pupils like his own children.

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 soul patch and a mustache. Eraqus's Keyblade Armor greatly resembles samurai armor, fitting in with his Japanese theme.

Master Eraqus physically resembles Hironobu Sakaguchi, 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 an open aversion to darkness, believing that it must be destroyed at all costs, and has at least partially ingrained these beliefs into his apprentices.

Despite his sometimes cold actions toward his apprentices, he still cares deeply for them. He has Aqua look after Terra as he travels the worlds because he is concerned for him, apologizes to Ventus and appears deeply pained before he attempts to attack the boy, and sheds a tear when he is forced to face off against Terra. Despite his relationship with Xehanort having been strained over the years, Eraqus seems to attempt to overlook his former friend's past actions to a degree. Even after he and Xehanort have a fight that results in Eraqus being scarred, he still asks Xehanort to watch over the Mark of Mastery with him. Following his apparent demise at Xehanort's hands, Eraqus "sets foot" into Terra's heart in order to help him counter Xehanort's possession and hopefully expel him from his body.

Abilities
Master Eraqus appears as a boss in Terra's storyline after the Keyblade wielder rescues Ventus from an attempt by Eraqus to kill him, and Terra is forced to fight him. 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.

Quotes

 * "Today you will be examined for the Mark of Mastery. Not one but two of the Keyblades chosen stand here as candidates... but this is neither a competition nor a battle for supremacy―not a test of wills but a test of heart. Both of you may prevail, or neither."
 * "If he were to―If those powers were to prove too powerful for him to handle, I want you to bring him back to me at once. It's for his own good. I could not bear to lose any of you to the darkness."
 * "I knew it. Xehanort―he could never let it go."
 * "Wait, Xehanort. There is a reason the precepts bar us from such knowledge. Why do you seek the χ-blade? Would you blanket all the worlds in darkness, reduce them to nothing?"
 * "Fool... You would risk an apocalypse out of sheer curiosity?"
 * "The χ-blade has no place in this or any world. Xehanort has made his purpose clear... and I am left with no choice. Forgive me... but you must exist no more."
 * "Why do all my attempts to reach you fail? If you don't have it in your heart to obey... then you'll have to share Ventus's fate."
 * "Has the darkness taken you, Terra?"
 * "No... you were right. I failed you, Terra. Perhaps I've no one but myself to blame for the darkness inside you. And now, I've done worse... raised my Keyblade against you and Ventus. My own heart is darkness!"