Here is the full list of all 20 Astral Heroes achievements.
Collect 400 cards
Collect 300 cards
Complete a Quest using a deck that contains no Creatures
Defeat a Quest opponent after summoning 3 Dragons during the battle
Collect 200 cards
Kill 100 vampires
Defeat a Quest opponent with no ally creatures on the board at the end of the battle.
Defeat a Quest opponent with 50 or more life remaining
Complete a Quest using a deck that contains no Spells
Summon 100 elves
Successfully rob 3 caravans
Defeat an opponent by dealing more than 20 damage with your final hit.
Win a Draft Tournament in the Online League
Successfully defend your guild caravan from the attack of another player
Join an existing guild, or create a new guild
Collect 100 cards
Win 10 matches in the League
Defeat a Quest opponent with 6 ally creatures on the board at the end of the battle
Complete 5 quests
Defeat an opponent using the attack of a Sheep as your final hit