From the publisher:

Gloomhaven Jaws of the Lion is a fully stand alone and cooperative campaign game of tactical combat set in the same unique fantasy world as its predecessor. Players will assume the roles of 4 new hardened mercenaries and work together to fight through a new prequel campaign full of choices, challenges, and twists. New built in tutorials, Learn-to-Play Guide, and play-surface scenario books allow players to jump into the action more quickly and easily than ever before. Playable as a stand-alone game or as an expansion to Gloomhaven.