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.
Explore 100% of the map.
Complete all villager sidequests.
Defeat Ulak.
Unlock all the Bestiary entries.
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.
Defeat King Trell.
Spend 5,000 gold.
Defeat the Titan.
Defeat 1,000 enemies.
Defeat the Bone Worm.
Defeat a boss without getting hit.
Defeat the Wendigo.
Defeat 100 enemies.