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