Here is the full list of all 20 Chasm achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Complete the game on Hard difficulty.
Complete the game as a Mortal.
Defeat a boss without getting hit.
Unlock all the Bestiary entries.
Explore 100% of the map.
Break all the crates in the game.
Complete all villager sidequests.
Defeat Ulak.
Find all the Journal Entries in the game.
Rescue all the missing villagers.
Defeat the Shaman.
Find all the Powerups in the game.
Defeat King Trell.
Spend 5,000 gold.
Become the Arena champion.
Defeat 1,000 enemies.
Defeat the Titan.
Defeat the Bone Worm.
Defeat the Wendigo.
Defeat 100 enemies.