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