Here is the full list of all 16 Cards and Castles achievements.
Unlock all 5 factions.
Lose a multiplayer game. It's ok, really!
Collect at least one legendary card!
Deal 10 or more damage in a single attack.
Destroy the enemy castle while the opponent has no units in play.
Craft 10 cards!
Craft one card using shards.
Win a multiplayer game.
Win 3 or more matches in a single draft.
End a turn with at least 6 buildings in play.
Win 10 multiplayer games.
Disenchant a card!
Collect 5 legendary cards.
Win a game with only 1 health left on your castle.
Deal 1000 total damage from attacks.
Craft 50 cards!