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.
Complete all villager sidequests.
Rescue all the missing villagers.
Explore 100% of the map.
Break all the crates in the game.
Defeat Ulak.
Find all the Journal Entries in the game.
Find all the Powerups in the game.
Become the Arena champion.
Defeat the Shaman.
Defeat King Trell.
Defeat 1,000 enemies.
Spend 5,000 gold.
Defeat the Titan.
Defeat the Bone Worm.
Defeat the Wendigo.
Defeat 100 enemies.