Myskina Acier

Two centuries back, Acier was a middle-aged man whose blond hair jutted upward across the front and gathered into a broad bun behind, worn under a scientist's coat over a green shirt. The 200 years he spent among dinosaurs left him swollen and decrepit, his garments reduced to rags and his hair wild, and he hid inside a dinosaur suit to pass among the beasts. Only after escaping Bonbori did he brew a serum that gave him back his former figure.

Devotion to family sits at Acier's core. He went to extremes to rescue Olga from a fatal sickness, and the death of his wife Livia left him grief-stricken. Learning that Olga had endured 200 years filled him with weeping joy, and he threw himself into Luffy's effort to free her, at one stage prepared to die in her place. After they made peace, he confessed a longing to spend happy days at his daughter's side, which left her blushing. He is also drawn to anything he finds cool, admiring the General Franky, and after his escape he picks up the manner of a giddy mad scientist, eager to run experiments over Olga's objections.

A masterful inventor, Acier produced the Pure Gold, a material that effectively renders anything in its vicinity immortal. Prolonged closeness to it inside Bonbori's belly froze his aging for two centuries, but, now severed from it and unwilling to make more, he will grow old again. His engineering also let him fill a mine with traps and explosives to guard the Pure Gold, and after his escape he formulated a slimming serum. Two centuries posing as a dinosaur taught him to talk with the beasts and with the water lizards of the fish's gut, though his frail body could be killed by a single hit from Luffy.

Long ago he lived contentedly on Alchemi with Livia and Olga until the girl fell to the incurable South Blue Emperor Fever. His relentless search for a cure yielded the Pure Gold, and a ring holding a fragment of it restored her health, but the substance's worth drew raiders and Livia was slain. Blaming her father, Olga cast her ring into the ocean, where the giant footballfish Bonbori rose to swallow it along with most of Alchemi, parting father from daughter. Believing Olga gone, Acier survived inside the creature dressed as a dinosaur.

When Heart of Gold opens, a dinosaur brings Luffy in as food, and Acier, stunned to meet a human and elated that Olga lives, joins the rescue. He tames a water lizard later dubbed Chavez, helps the crew cross Bonbori's stomachs, and reaches Alchemi, laying eyes on his daughter after two centuries apart. He drops her and the Straw Hats through a trapdoor to safety and faces Mad Treasure alone, even trying to blow up the mine with them both inside. After Luffy beats Treasure, the two reconcile, and as Bonbori heaves the group out they watch the Pure Gold sink into the fish's lamp. Swearing never to make it again, Acier returns to life with Olga and markets his restorative serum as a weight-loss product.