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