Master Eraqus

Master Eraqus is the 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. 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 turns his attention to Ventus and prepares 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.

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 x blade, the weapon that sparked the Keyblade War and the means Master Xehanort intends to use to fulfill his goals. 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.