When realms are generated, they remain generated as long as a portal connects with a specific card/difficulty combo and are not reset. Propose building a device in a realm that works similarly to an estate but requires at least 2 players to build, and no more than 8 (assuming that is the multiplayer limit in a realm). This device would then keep that realm persistent and connected as long as at least 2 players have a portal connected to that same realm. Allowing for a community building space.