Zeromus [zɪˈroʊ.məs] is a powerful voidsent from the Thirteenth that serves as an antagonist in Final Fantasy XIV: Endwalker patch 6.5, "Growing Light".
History[]
Zeromus is formed.
After the Warrior of Light defeated Golbez, the latter threw the unconscious body of Azdaja, transformed into the Shadow Dragon, into the chasm on the moon of the Thirteenth. What remained of Zodiark's aether merged with it, resulting in the creation of Zeromus, whom Golbez named as such after an ancient hero. Zero attempted to attack and seal off Zeromus, but her offense had no effect and she was knocked back.
Y'shtola noticed with alarm that their warding scales began to flash, signifying that they may not hold up against a voidsent born of such circumstances, and the group retreated on Vrtra's back. Golbez mused that Zeromus was not strong enough yet to breach the barrier between worlds, considering that it was newly born.
The group returned to the void and breached the veil of darkness using resplendent Light they acquired from the First. Though the Warrior and their allies clashed with Golbez, who aimed to prevent his goal from being thwarted, they reached Zeromus's dwelling and confronted the dark being. Despite its immense power, making cracks in the fabric of reality, the Warrior defeated it, but it swiftly regenerated, as per its nature as a voidsent. With the aid of their allies and a swayed Golbez, however, they destroyed Zeromus, with Zero sealing its aether into memoria while Vrtra called to Azdaja, freeing her from Zeromus's grip.
With the threat passed, Zero bequeathed Zeromus's memoria to the Warrior so that it would be delivered to Ryne, so its immense Darkness would help restore balance to the First.
Characteristics[]
When it was formed, Zeromus's appearance was that of mass of darkness protruding arms and a head. Beneath it, Zeromus's appearance is similar to its original appearance from Final Fantasy IV.
In accordance with the nature of voidsent to take on the characteristics of those they are fused with, Zeromus's desire to break the barrier between worlds was fueled by Azdaja's longing to return home to the Source. Zeromus speaks with Azdaja's voice in the language of dragonkind.
Gameplay[]
Zeromus is the boss encounter of the trial 
The Abyssal Fracture and its high-end equivalent The Abyssal Fracture (Extreme).
Behind the scenes[]
Zeromus is based on the final boss of the same name from Final Fantasy IV where he is the manifestation of the hatred of the lunarian Zemus, which became sentient after Zemus was killed. Right after Zeromus emerged, he could not be harmed by normal means due to lacking a physical form. Zero's inability to harm it in Final Fantasy XIV is a reference to this.