EA has announced Shadow Realms from BioWare Austin.
Set in a modern fantasy world, it features online 4 vs 1 gameplay, with you and your party against another human player called a Shadow Lord (basically Dungeon Master).
The gameworld will constantly change – perhaps procedurally generated – but the overarching narrative will be released episodically.
Shadow Realms will be available  for PC next year, but you can sign up for a closed alpha next month.