The Jaws of the Lion Add-on for Gloomhaven has 11 achievements.
Complete all Jaws of The Lion side scenarios
Loot all the treasure chests from Jaws of the Lion scenarios
Win a scenario with only mercenaries from Jaws of the Lion in your party
Have the Hatchet use The Favourite in 5 or more attacks in a scenario
Have the Demolitionist destroy 8 or more obstacles in a scenario
Have the VoidWarden grant 10 or more actions to other mercenaries in a scenario
Level up to 5 or more all the new Jaws of the Lion classes