Master Eraqus is fought only in Terra's storyline, when the Keyblade apprentice is forced to battle his master in order to save Ventus. Master Eraqus had attempted to destroy the boy to prevent the creation of the χ-blade, but Terra refused to let him hurt his friend, and submits to the darkness in order to protect Ventus. After Eraqus sheds a single tear, the two fight a climatic battle in which Terra is the victor.
Master Eraqus's attacks are primarily quick, Physical or Fire techniques, and are shared with his Keyblade Armor.
Master Eraqus is one of the most powerful bosses fought in Terra's scenario. His attacks are mainly light-based, but he can also use fire to a degree and favors fast-paced physical attack combos, as well. Terra has access to Shotlocks but not Dimension Links in this battle, and his arsenal of Command Styles is limited, as he only has access to the slow but powerful Dark Impulse. It is because of Dark Impulse's power that Shotlocks should not be needed, regardless of their availability. However, the player should not be reckless during the battle, and he or she should only follow a hit-and-run strategy.
At the start of the battle, Terra will instantly gain access to Dark Impulse. It is at this point that the player should begin hammering Eraqus with physical attacks, careful to use Slide in order to escape Master Eraqus's upward slashes, which he tends to use at close range. Eraqus may also begin to use a Sonic Blade-like attack or another basic, multi-hit combo, both attacks avoidable with the Guard and Counter Hammer combo. Counter Hammer will deal great damage to the boss, opening him up for more damage as he is knocked off his feet. The player can then run farther away from the boss as he recollects himself, dealing damage with a long-range attack such as Dark Firaga, or they can immediately close the gap between Terra and Eraqus with Chaos Rave. Beware that the farther away Terra is from the boss, the higher the chance there is of him using a desperation attack to deal heavy damage to his old apprentice.
Eraqus may surround himself with blade-like energy beams, the area around him glowing with light. He will then fire these long-range projectiles at Terra. These beams can only be defended against with Guard, the benefit of guarding being the fact that the beams will then be deflected back at Eraqus to deal damage. When Eraqus fires several spheres of light energy at Terra, the same can be done. If Eraqus surrounds himself with more blade-like energy beams and leaps into the air, sending them into the ground, chain several Slides together to avoid the homing columns of fire he summons.
Keep at the hit-and-run strategy, and Master Eraqus will go down in time. Curaga can be used if one is at low health, and one should use whatever darkness-based abilities in Terra's arsenal that have been equipped in order to fill the Command Gauge and speed up the accessing of Dark Impulse. While running away from Eraqus will cause the Command Gauge to quickly empty again due to a lack of constant attack, the player should use the Dark Impulse finisher as soon as it appears as a Deck Command. This will ensure Terra escapes damage from attacks as he sinks into a pool of darkness, dealing heavy damage with a dark hand as he re-emerges. Mine Circle can be used to trip Eraqus as he chases after Terra, opening him up to more damage.
Since most of the commands can leave you open to an attack in this battle (because Eraqus tends to counter right away), another idea would be to exchange all Attack Commands with Healing Commands and solely using the regular Attack to take him down. This proves rather useful in Critical Mode. With patience, powerful attacks, and a lack of recklessness, Eraqus will fall with relative ease.