Here is the full list of all 14 Creature Card Idle achievements.
Unlock the Haunted Woods expansion
Earn 100K gold in Intro Realm
Have a sheep call a Meteor to the center of the earth
Empower a Crab in Intro Realm
Earn 1K gold in Intro Realm
Earn 10M gold in Intro Realm
Buy 100,000 5-card packs in one go
Earn 25+ gold/sec with only Ghouls
Ascend, earning at least one gem, for the first time
Unlock the Underworld expansion
Earn +500 wood/sec with only Lil' Lumberjacks and Hatchets
Unlock the Plains of War expansion
In Plains of War, kill the Scarecrow in one hit
Kill a Dead Fish in 4 or more rounds