It's called the Mata Nui Online GAME (MNOG), and you can find an archived version that plays locally on your computer here: https://biomediaproject.com/bmp/play/web-games/mnog/
And if you go here, you can find a lot of other Bionicle games, including the 2nd MNOG.
Is your setup such that when you are not at home, traffic routed to your wireguard_in network reaches out to the Internet through wireguard_out? Idea being your mobile devices effectively use the same mullvad connection they would if you were at home.