Zac is the product of a toxic spill that ran through a chemtech seam and pooled in an isolated cavern deep in Zaun's Sump. Despite such humble origins, Zac has grown from primordial ooze into a thinking being who dwells in the city's pipes, occasionally emerging to help those who cannot help themselves or rebuild the broken infrastructure of Zaun. Zac has an innate ability to feel the emotions of others due to his properties, often feeling overwhelmed by too many positive or negative emotions. Due to his upbringing from his adoptive parents, Zac has a kind, optimistic outlook on life and enjoys helping others, though when there are negative emotions around him he stops to intervene at best and lashes out in destructive tantrums at worst. He was overcome by rage towards his parents' deaths in the hands of Saito Takeda's men, yet felt remorse for the destruction he caused during his outburst, rebuilding everything he's damaged before choosing to live in the sewers alone. He feels a strong aversion to violence around him, yet usually remains in a calm demeanor when he fights.