Here is the full list of all 51 Mythical Mayhem Playtest achievements.
Lose the game before turn 10.
Win the game before turn 10.
Get 2 Fortune Runes when gambling.
Get all 3 Fortune Runes when gambling.
Draw two Ambitions back to back.
On a victory all of your best tracked rounds were less than 5 turns before game end.
Win the game at turn 45+.
Win 7 consecutive battles.
Draw a hand of all Wounds.
A Wolf eats a 6 Cost+ card.
A Bird snatches a 8+ Cost card.
Draw every card from your deck.
Kill a luck hound.
You arrested the cat.
Complete the Long Arm of the Law quest and have more than 2 Heroic Deeds.
Win a game with 6+ Dark Deeds.
Win a game with no Heroic or Dark balance and no Dark or Heroic Deeds.
Kill a Unicorn.
You ate a cat.
Beat Zurter using Brave Conquest (win the scenario by beating him in battle) without having a blue hero anywhere in play.
Have 2 Infinity Tomes in play.
Have Xavier's dad save Xavier from the halflings.
Successfully battle 3 or more Mountain Apes.
Have 2 or more Vicious Temper cards in play.
Create a campaign hero.
Win the Campaign with every completed quest being a Brave Conquest.
Win the Campaign with every completed quest being a Heroic Victory.
Upgrade a custom hero to a card cost of 7+.
Finish Campaign Chapter 1.
Finish Campaign Chapter 2.
Finish Campaign Chapter 3.
In the Campaign kill the dragon Mayhem.
In the Campaign successfully win the Mythical Trial quest with a Heroic Victory.
Have 33+ heroes at the end of the Campaign.
Win the Campaign without ever recruiting a hero.
Upgrade the gambling hall twice.
Unlock all the Campaign market stalls.
Have 4 beds in the infirmary.
Beat the Campaign with 5+ Dark Deeds.
Beat the Campaign with 5+ Heroic Deeds.
Beat the Campaign with 0 Heroic Deeds and 0 Dark Deeds.
Fully upgrade the stables.
Have 1000+ Campaign Resources.
Beat the Campaign on Hard difficulty.
In a Campaign game play the Shadow Ninja card.
Complete 20+ Side Stories.
Rascal activates his Unholy Tenacity 3 times in a single game.
Play the Clockwork Shotgun card.
A hero perishes in the Campaign.
Upgrade a Campaign card to use an Allegiance.
Unlock the Mysterious Stranger.