Isekai Key

You have been given a magic key that allows you to visit numerous worlds across the multiverse. You can use it to travel to any universe you wish. Only catch is that once you arrive in another world the key cannot be used for a whole year. They key can be used on any door that has a keyhole. You can bring anything or anyone with you on your adventures as long as they can fit through the door you use the key on. Beware, other people may try to steal your key to use for their personal gain. If you lose it you'll be trapped in whichever universe you're in.