Here is the full list of all 19 Ancient Gods achievements.
Back to town using Portal after the third loop in endless mode
Kill an enemy with 100% HP by one card
Have a 1.000.000 damage hit to the enemy
Inflict at least 1000 negative effects on an enemy in one turn
Pass 3 loops constantly in endless mode without gaining any block
Pass 2 loops constantly in endless mode without adding any card to deck (Except cursed card)
Pass 1 loop in endless mode without using campfire
Have at least 20 cursed cards in your deck
Remove at least 10 cursed cards at once with Cleansing Fountain
Pass 1 loop in endless mode without having any cursed card
Gain at least 1000 combo of any type in your first turn
Gain at least 100k block in your first turn
Play every God
Activate all cards in card library (Except unique card)
Have all Gods with all classes unlocked and maxed enhancement
Win against Gambler 3 times in a row in endless mode
Escape from trap 2 times in a row in endless mode
Activate at least 24 cards in one turn
Build your deck with at least 200 cards