Dario Montoya stood as Princess Sara Vazelia’s unwavering protector and a Makai Knight of the Kingdom of Vazelia, bearing the title Zem the Obsidian Knight. His devotion to Sara shaped his every choice, first as her guardian during combat drills where his unmatched prowess solidified his reputation as the kingdom’s greatest warrior. During a Horror’s assault on the castle, he shielded Sara from its jaws, though its venom scarred her visage, plunging her into anguish and madness. Consumed by remorse for failing her, he gouged out his eyes to stay at her side without subjecting her to shame.

When Sara ignited the kingdom’s ruin and leapt into a lake to end her life, the Horror Nigra Venus claimed her. Dario, resolved to uphold his oath, plunged after her, merging with the entity to become Sir Venus—a fallen knight twisted by a desperate quest to resurrect Sara’s beauty, even as he abetted her rampages.

Years later, he surfaced as an enigmatic ally to León Luís, thwarting Nigra Venus’ minions and steering him to save Roberto. Yet his allegiance remained tethered to the Horror, as he orchestrated sacrifices to awaken Zirkel’s Ring, a relic poised to fracture reality. In battle, he wielded his Makai Spear with lethal precision, leveraging parkour agility honed despite blindness, while his Madō Horse Raimei thundered across terrains. Ultimately, he fused wholly with Nigra Venus, their bond detonating in a cataclysmic clash that erased both.

His skills—Makai combat mastery, blinding-speed acrobatics, and symbiotic command over Raimei—mirrored a legacy of loyalty warped into ruinous fixation, sealing his fate as a guardian who became the Horror he vowed to destroy.