This guide will just list the game's current achievements. If more are added I might update. Currently there are 31 achievements: 15 visible and 16 hidden.

First section will list visible achievements. Second section will list hidden. I will provide some tips.

Hunter
Defeat a Boss on Easy or higher Difficulty.



Giant Slayer
Defeat a Boss on Medium or higher Difficulty.



Bossing It!
Defeat a Boss on Hard or higher Difficulty.



Milk Run
Complete an Adventure on Easy or higher difficulty.



Gauntlet
Complete an Adventure on Medium or higher difficulty.



Trial of Fire
Complete an Adventure on Hard or higher difficulty.



Brave
Complete an adventure at any Cataclysm difficulty level.
Cataclysm can get tough, and if you're used to playing on lower difficulties you'll be taken by surprise a lot. Consider that enemy cards will end up being buffed, there will be more of them and they will have more health. My go to team for all Cat difficulties was Assassin/Warrior/Warlord. Stack card draws on the Assassin and take smoke bomb as soon as you can so that your party doesn't take massive damage on the first turn from ranged enemies. Certain items like the sword that allows multiple redraws, or the one that picks up an extra card after 3 are played work well here.
If you are worried about being under-levelled for a boss fight, don't be. The largest issue will be gear. I did my Cat playthroughs by doing the Beacon of Hope quest repeatedly, and would defeat the final boss on level 4-5 easily if I had good gear. Depending on your luck the fight will be harder though. Make good use of stealth and stack damage bonuses on your Assassin, and aim to get some bash and hamstring cards for the Warrior and Warlord. The Warlord's Attack and Bolster cards are also vital.



Foolhardy
Complete an adventure on Cataclysm 5 difficulty or above. Refer to advice given for "Brave".



Zealous
Complete an adventure at Cataclysm 10 difficulty level. Refer to advice given for "Brave".



Awoken
Raise a Class's Soul Level to 5.



Ascended
Raise a Class's Soul Level to 10.



Assassin
Defeat 50 enemies in combat.



Destroyer
Defeat 100 enemies in combat.



Reaper
Defeat 200 enemies in combat.



Death Incarnate
Defeat 500 enemies in combat.

Lord of War
Unlocked the Warlord class.
All Class unlocks will likely happen as you play, but you can check the requirements for each one. Some unlock from completing adventures, some side quests, etc.



Chemistry Major
Unlock the Alchemist class.



Wiccan
Unlock the Witch class.



Killer for Hire
Unlock the Assassin class.



Spirits’ Fury
Unlock the Spirit Speaker class.



Scion
Unlock the Occultist class.



Tried and Tested
Complete the ‘Trial of Fire’ quest on any difficulty.
This is the "main" quest.



Saviour
Complete the 'Water Gem' quest on any difficulty.



Shining
Complete the ‘Beacon of Hope’ quest on any difficulty.



Godlike
Complete the 'God Hunter' quest on any difficulty.



Patron
Complete the ‘Cursed Sonata’ quest on any difficulty.



Strong
Deal 10 damage on an enemy with a single attack.
Any of the damage achievements can easily be gotten with either the Hunter or Assassin. Stack a few perfect aim cards on either and you're good to go. The Assassin can be stacked with stealth, battle trance, versatility, lethality and with a critical strike card you should do easily 50 damage.



Mighty
Deal 20 damage on an enemy with a single attack.



Herculean
Deal 30 damage on an enemy with a single attack.



Nuclear
Deal 50 damage on an enemy with a single attack.



Scraped Through
Win a battle with one remaining hero with only 1 health.
This might come to you by chance, but if not that's okay. Just start a game on easy, find a battle and defeat all but one enemy and then let two of your heroes be defeated. It might take a couple tries for the health to work out correctly, but it's not too difficult to let your final hero take a few hits from a charred until they are on 1 health.

Hopefully this guide was at least somewhat helpful. None of the achievements are super secret or anything, I just know I like to know if an achievement is something I'd never find on my own before going for 100%.

If you're having trouble with the higher Cat difficulties, just try to slow down and think through the order of operations, both in combat and in the overworld. For example, doing the Beacon of Hope quest is helpful because it's short, and has a number of quest specific events and battles that make it easier to anticipate a winning strategy. I liked to go Human Ruins - Elfish Ruins - Shop because I knew what I needed before each step, and I had a good idea of the rewards for doing each step.

Anyway, continue enjoying the game. It's well made and fun, feels like I'm playing single-player DnD.