Here is the full list of all 16 The Fox in the Forest achievements.
Win a normal-length game with exactly 21 points
Win all 13 tricks in a round.
Win 0 tricks in a round.
Play three Swans in a round.
Swap the decree with a Fox two times in one round.
Discard a Monarch with a Woodcutter.
Win two Treasures in the same trick.
Win a trick where your Witch defeats a Monarch.
Play a Monarch on the last trick of a round.
Win an online game.
Win 10 online games.
Win 50 online games.
Win 100 games in any mode.
Complete the "Once Upon a Time...." Challenge on Normal Difficulty
Complete the "Dark Woods" Challenge on Heroic Difficulty
Complete the "Meeting the Witch "Challenge on Heroic Difficulty