Nightingale takes place in an alternate history Victorian era, around the year 1889, in which the world is split up into many different realms. The game's setting is "Gaslamp Fantasy", which features magic, mystery and fantasy races.
Realms are connected by portals, with the city of Nightingale as a main hub.
Realms are described as "open-world".
Fast travel mechanics have not been confirmed, other than Portals.
Players will be able to make a realm their home and explore other realms from there.
Realms vary in difficulty, and some might need specific gear or a group of players to explore, but yield better rewards.