In the Extended continuity, Excalibur and the Aegis Shield are Hikaru‘s Paladin weapons, acquired during the infiltration of Castrum Centri. Where she had been using traditional swords and shields up until then, Excalibur and the Aegis Shield are special; because she attuned to them upon touching them for the first time, their strength will scale with her. Never again would Hikaru have to replace her equipment or even perform maintenance on them, as Excalibur’s blade would never dull, nor would the Aegis Shield show any visible sign of wear and tear.
Both Excalibur and the Aegis Shield bear a red gem; Excalibur’s gem is located on the upper part of its grip, where the Aegis’ is located in the dead center. The gems serve the same function as a modern soul crystal, but are capable of acting as vessels for living souls in addition to accumulating the user’s experience. They collectively serve as the true catalyst for Hikaru’s Paladin job, with each gem contributing a different set of abilities and traits.
The Extended continuity completely redoes their origins as well. Both the sword and shield were previously ancient Ivalician treasures, wielded by the royal family during times of war and otherwise used in ceremony. When Agrias took leave of her position as Princess Ovelia’s personal bodyguard to join the Warrior of Light of that era (the original Ramza Beoulve), Ovelia had Excalibur and the Aegis Shield brought out of storage and gave them to Agrias, believing they would be more useful in her hands than sitting in a vault.
When Ramza’s party failed to defeat the High Seraph Ultima, and the surviving party members gave up their bodies to power the seal, Agrias was the last to undergo the ritual. However, Ultima was able to get off one last strike, cleaving Agrias’ soul in two. One half was drawn into the Aegis Shield’s gem, while the other half became a mindless phantasmal entity that would wander the Orbonne Monastery for multiple centuries, becoming a feared subject of many tales meant to dissuade tomb raiders from approaching.
Excalibur and the Aegis Shield would eventually make their way into the custody of the Garlean Empire, though they were deemed unsuitable for use by pureblooded Garleans. Anyone who attempted to handle them would experience painful feedback, owing to the user’s biological inability to manipulate aether. The sword and shield were transferred to Castrum Centri’s Foreign Armaments Containment, where they would remain until Hikaru and her allies infiltrated the facility during A Realm Reborn. Upon sensing Hikaru’s presence, Agrias called out to her and after convincing Hikaru she was not a ghost, she beckoned Hikaru towards the containment pod that held Excalibur and the Aegis Shield. Agrias explained that she was once a flesh-and-blood person and had been drawn into the Aegis Shield, having lost over half of her memories. When Hikaru used a provided passcode to release the sword and shield from containment and touched them for the first time, it established a spiritual link that would relay her vision and hearing to Agrias. In exchange, the weapons would become nearly weightless in Hikaru’s hands, and she would acquire greater mastery over light.
During the Return to Ivalice raids in Stormblood, Hikaru confronts the Phantasmal Holy Knight that contains the other half of Agrias’ soul and memories. After defeating it, Hikaru draws its aether into the Aegis Shield, effectively stitching Agrias’ soul back together and restoring her full memory. As it functionally constitutes a “rejoining,” the Aegis Shield becomes the Rejoined Aegis Shield and casts an intense golden glow.
In the Extended continuity’s version of Shadowbringers, Ardbert allows himself to become one with Excalibur, as merging with Hikaru is not an option at the time. Similar to the Aegis Shield, Excalibur becomes the Rejoined Excalibur and acquires the same golden glow.
The evolution of both weapons also affects the potency of Hikaru’s Light Dragon Ruination Limit Break. On top of that, there is a chance either Agrias or Ardbert (or rarely, both at once) manifesting to augment the final hit of the attack sequence.
A version of Excalibur and the Aegis Shield exists on the First, originally used by Hikari (the First shard of Hikaru, and Kiros‘ elder sister). The two were obtained during the exploration of Nabaath Araeng’s royal palace. Only Excalibur survived as of Shadowbringers, with the Aegis Shield having been destroyed when fighting Forgiven Narcissism. Unlike the Source version, the sword and shield lack a golden glow. Kiros carries his sister’s Excalibur on him but does not typically wield it himself. To differentiate from the Source version, the version from the First is dubbed Parallel Excalibur.