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, when he is introduced to a young Ventus after Eraqus's long-time colleague Master Xehanort arrives at the Land of Departure to witness Terra and Aqua as they endure their Exams. The exam is carried out soon afterwards, 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 the man 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. Meanwhile, Terra receives this news from Master Xehanort and also learns that Eraqus plans to eliminate his friend, the man tricked into thinking that the only way to save Ventus from his grim fate being to eliminate his master. Terra arrives just before Eraqus is about to vanquish Ventus, Eraqus sensing that Terra has indeed descended into darkness. Seeing Terra's stained heart, he recalls a long-ago discussion between himself and Master Xehanort over the Keyblade War during which Eraqus disagreed with Master Xehanort's hypotheses and wanted to fight Master Xehanort for it. Master Xehanort responded by attacking Eraqus and leaving him with the scar he presently bears.

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 another world by Terra. Terra no longer caring that Eraqus is his master and someone he holds dear, Eraqus battles him. 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 fades out of existence. 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. Master Xehanort then realizes that Eraqus's heart now resides within Terra, with the two beginning to debate over who would control it.

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.

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, the weapon that sparked the Keyblade War and that Master Xehanort desires. 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.

He also feels strong attachments, having Aqua look after Terra as he travels the worlds, apologizing before his assassination attempt on Ventus, and even shedding a tear when he is forced to face off against Terra. Eraqus has a strong sensitivity to betrayal, having experienced it far too many times in his life, both at the hands of Master Xehanort and Terra, himself.

Fighting Style
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, grey in coloration. It has the appearance of an old fashioned skeleton key, the teeth shaped like an "E". Its Keychain is the Keyblade "Mark of Mastery". He summons his Keyblade in a fashion similar to Terra, shrouded in a series of golden blocks.

Trivia

 * In the English version of Kingdom Hearts Birth by Sleep, Master Eraqus is voiced by Mark Hamill, who was specifically chosen by Tetsuya Nomura for his role as Luke Skywalker in Star Wars.
 * 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 of neither"

"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' fate"

"Has the darkness taken you, Terra?"

Notes and references
Maître Eraqus Maestro Eraqus