Before Kingdom Hearts Birth by Sleep
After passing the Mark of Mastery 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. Then 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 in Terra and Aqua before taking Ventus under his wing from who he thought was a 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 confines 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 revealed 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 literally stabbed behind the back 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 vessel, he learns that Eraqus entered Terra's heart and thus gives him the means to resist Xehanort.
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.
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.
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.
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.
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