The Wizarding World
Ever since Tom Riddle had been resurrected and captured, the European Wizarding World had become much more peaceful. During Hermione's fifth and sixth years, Karn had returned once or twice, mainly to collect some Magical Creature ingredients for experiments, while also checking on Hermione and Pheobe and taking his goddaughter on trips elsewhere during the summer holidays.
After their trips, he would take a batch of potions Hermione had brewed. Although many were useless to Karn, they were still fairly useful to his subordinates in other worlds. Felix Felicis also continued to work quite well on him, giving Karn some pleasant experiences.
Besides that, Karn had continued to push the development of Goblin industry. Flying broomsticks were merely toys for students. If the Goblins did not want to disclose their alchemical craftsmanship, they had to follow Karn's ideas and requirements.
Flying skiffs, flying warships, and the like were the direction Goblin craftsmanship needed to develop in. Alternatively, Karn would have the Goblins modify and enchant airships equipped with modern weapons, increasing their speed and protection and adding the ability to automatically repair physical damage.
Flying skiffs powered by an Arc Reactor would already be very fast. With magical acceleration on top of that, their speed could break through another limit, and Protective Charms would keep them from being damaged. That was the appeal of speed combined with technology.
Karn planned to incorporate alchemical craftsmanship into many parts of his aircraft carriers. Some work would be entrusted to the Goblins, while he would do some himself.
During Hermione's fourth year, the Goblins had still been unwilling to accept Karn's commissions, but a year or two later, their entire race had yielded.
Karn's Magical Ingredients Shop had opened branches in eight European countries. He had monopolized thirty-six commonly used