Here is the full list of all 12 Grimcastle: Battle Tales achievements.
Fight 10 battles
Defeat 3 demons
Defeat 3 assassins
Defeat 3 paladins
Deal 1000 damage
Score 2 critical hits
Dodge the attack
Reach level 5
Reach level 20
Go through the campaign as an assassin
Go through the campaign as a paladin
Go through the campaign as a demon