Eraqus

Eraqus, known to his students as 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.

Development
Master Eraqus was conceived as a Final Fantasy-esque counterpart to Disney's Master Yen Sid, given that his name is an anagram of "Square", a reference to Square Enix, the developers of the Kingdom Hearts series, and his resemblance to Hironobu Sakaguchi, the creator of Final Fantasy mirrors Yen Sid's name being an anagram of his creator's name, Walt Disney. Tetsuya Nomura once forgot the basis of Eraqus's name, and had to be reminded by an employee that it was an anagram of "Square".

In the English version of the series, Eraqus is voiced by Mark Hamill, who was chosen specifically by Nomura because of his role as Luke Skywalker, his love of the Star Wars series, and his desire to pit Star Wars and Star Trek (a series that Nomura is also a fan of) against each other in a "dream match" by casting Star Trek's Leonard Nimoy as Master Xehanort, Eraqus's friend turned rival.

Before Kingdom Hearts Birth by Sleep
After passing the Mark of Mastery exam his master placed him through, Eraqus became a Keyblade Master and was entrusted to safeguard the Land of Departure while his fellow apprentice made master, Xehanort, left to travel the worlds as a Seeker. When the two meet again, Eraqus learns of Xehanort's scheme to cause a second Keyblade War in order to recreate the χ-blade and attempted to fight his former friend to stop him from carrying out what would destroy everything. However, his attempt was futile as Xehanort quickly took him down and scarred his face. Years later, Eraqus obtains apprentices of his own, Terra and Aqua, before taking Ventus under his wing from a seemingly repentant Xehanort.

Kingdom Hearts Birth by Sleep
Eraqus holds the Mark of Mastery exam for Terra and Aqua, with Ventus and Xehanort as witnesses. In the end, Eraqus names Aqua master while refusing to give Terra the mantle on the grounds that he is unable to control his darkness. Despite the formality, Eraqus confides to Terra that he has the potential to become a Keyblade Master. Little does Eraqus know that Xehanort had used his dark powers to tamper with the course of the Exam itself. Soon after, he conveys to Aqua the responsibilities that go with her status and what she is required to do if he died for any reason. With Xehanort no where to be seen, 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.

Upon seeing Ventus later returning, Eraqus welcomes him back home with open arms, only to find the boy confused and enraged as he questions him about the χ-blade and his role in its creation. Eraqus, realizing that Xehanort never intended to give up his agenda and revealing to the boy his role in the plot, sees killing Ventus to be the only way to put Xehanort's plot to an end for good. However, Xehanort arranged Terra to arrive to save Ventus from Eraqus. Sensing that Terra has indeed descended into darkness, the youth refusing to let him kill Ventus, Eraqus is left with no choice but to eliminate them both. However, after throwing Ventus into a portal leading to the Destiny Islands, Terra mortally wounds Eraqus. In the end, Terra regretting fighting him while he sees that turning his Keyblade on his own apprentices was an error on judgement, Eraqus is impaled from behind by Xehanort and fades in Terra's arms.

Avenging Eraqus's death was among Terra's primary motives for defeating Xehanort during the events in the Keyblade Graveyard. However, after Xehanort uses Terra's body as the first of his vessels, he learns that Eraqus entered Terra's heart and thus gave him the means to resist Xehanort.

Kingdom Hearts III
In the E3 2015 trailer for Kingdom Hearts III, a young Xehanort and Eraqus are playing chess, discussing about the Keyblade War. When Xehanort mentions the "Lost Masters" actually started the war, Eraqus feigns ignorance, and Xehanort remains unconvinced.

Where Xehanort muses on how on the land where the Keyblade War was fought, darkness will prevail and light expire, while Eraqus counters him by claiming that the light might surprise Xehanort and prevail, and Xehanort expresses interest in this possibility.

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 and almost bigoted 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 influence and strength settles within Terra 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's Defender", 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. In battle, he holds his Keyblade in the stance.