Here is the full list of all 20 Dark Gates achievements.
All heroes are dead, game over
Gather 5000 in gold
It's alive!
Scare a monster
Party is dead
Kill one hero
We want no trouble
Upgrade a hero
Successfully negotiate with a monster
Successfully bribe a monster
Reset the game
Save a party layout for next time
Save Game
Land a maximum damage hit
Land a critical hit
Read HowTo
Destory Dark Gates on easy difficulty
Destory Dark Gates on normal difficulty
Destory Dark Gates on hard difficulty
Kill the Unnamed