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 combat [North Korea’s] use of illicit activities—including cyber crime and cryptocurrency theft—to generate revenue for the regime.”