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 as a Mortal.
Complete the game on Hard difficulty.
Defeat a boss without getting hit.
Unlock all the Bestiary entries.
Complete all villager sidequests.
Explore 100% of the map.
Find all the Journal Entries in the game.
Break all the crates in the game.
Rescue all the missing villagers.
Defeat Ulak.
Defeat the Shaman.
Defeat 1,000 enemies.
Find all the Powerups in the game.
Become the Arena champion.
Defeat King Trell.
Spend 5,000 gold.
Defeat the Titan.
Defeat the Bone Worm.
Defeat the Wendigo.
Defeat 100 enemies.