Ice Oni

Ice Oni started as a man-made illness that Queen bonded with a chilling gas and then fed into his Excite Bullets to make it a weapon. He called the result his masterpiece and prized it over the rest of his research. Its purpose was cold-blooded: the Pleasures and the Waiters, the two lowest divisions, had forfeited any shot at SMILE powers and were treated as disposable, so the virus was built to wring a brief spell of combat value from them before their lives ran out.

When the frozen gas gets into someone, the pathogen breeds within them, frost climbs over the skin, and the head and limbs sprout the horns, fangs, and claws of a folklore demon. Judgment fails and the host turns feral, striking allies and enemies without distinction while muscle mass swells to grant brutal strength and toughness that resists conventional attacks; Hyougoro, for one, reclaimed his prime-era body. Zoro compared their resilience to the undead, since a felled victim rises again at once. The strain kills in about an hour, and transmission runs body to body through touch, even by a bite, so anyone fighting the infected must use an object to keep skin clear of them. Brook, having neither flesh nor blood, walked away untouched. The lone remedy was a single antibody sample Queen held, from which Chopper eventually cultured an airborne countervirus, the Chopperphage, able to dose entire crowds. Proximity to fire, including Marco's phoenix heat, could stall or roll back the freezing too, though only for a while.

Queen turned the disease loose during the war on Onigashima's Live Floor. Once X Drake switched sides, the scientist swept the assembled samurai with a gatling gun loaded with the virus rounds, aiming to seal the chamber and infect all present. He gleefully lobbed the only antidote vial to Scratchmen Apoo so the room would fight over it. Chopper, Hyougoro, Omasa, various samurai, and rank-and-file Beasts Pirates all fell sick. Zoro smashed the gatling gun in a rage, Marco's flames granted a reprieve, and Chopper, with Miyagi and Tristan, completed the gaseous cure that cleared the floor.