Lacua, a demon serving Violet, was assigned to observe Raja's royalty and report when their magic tiara created a perfect vessel for his master. His impatience drove him to violate Violet's contract by actively manipulating events to accelerate the curse. Disguised as a traveling merchant dealing in rare gems, he frequented Raja to monitor the queens while orchestrating schemes from behind the scenes. Preferring political maneuvering and psychological manipulation over direct combat, his methods reflected a cowardly and impatient nature. He collaborated with Chikuan, another demon posing as an elf doctor, to weaken Queen Towa. Their actions included poisoning Raja's lake, spreading false rumors to incite invasions, and coercing individuals like Hiiro into swallowing forbidden "Cursed Orbs" – transforming them into uncontrollable "Mad Ogres" to escalate chaos. Lacua reveled in others' suffering, often expressing dramatic amusement at tragic situations while maintaining a polite facade. As a Demon Duke, Lacua possessed significant combat abilities, wielding magical energy blasts and a diamond-shaped purple crystal that transformed into a sword. His overreach drew Violet's ire, resulting in his abandonment when Rimuru Tempest intervened. In a final act of desperation, Lacua swallowed a Cursed Orb himself and unleashed "Nuclear Flame" to destroy Raja, but Rimuru absorbed the attack and consumed him entirely. His actions extended into the film *Scarlet Bond*, where his unfinished curse circle in Raja's lake was later revealed as a prototype stolen from Violet. Spin-off media, including mobile games, depict Violet complaining about Lacua as a "useless subordinate."