Created by a Vietnamese gaming studio, Axie Infinity offers players the chance to breed, trade and fight Pokémon-like cartoon monsters to earn cryptocurrencies including the game’s own “Smooth Love Potion” digital token. At one stage, it had more than a million active players. But earlier this year, the network of blockchains that underpin the game’s virtual world was raided by a North Korean hacking syndicate, which made off with roughly $620 million in the ether cryptocurrency. The crypto heist, one of the largest of its kind in history, was confirmed by the FBI, which vowed to “continue to expose and...