Here is the full list of all 35 Avernum 2: Crystal Souls achievements.
Complete all three game-winning quests in Avernum 2 and never set the difficulty below Normal.
Complete all three game-winning quests in Avernum 2 and never set the difficulty below Hard.
Complete all three game-winning quests in Avernum 2 and never set the difficulty below Torment.
Slay the commander of the invading army.
Fill up a spirit prism.
Keep the Empire from flooding Avernum with troops.
Learn 20 mage spells at level 3.
Learn 20 priest spells at level 3.
Win Avernum a powerful ally in its war.
Get a really sweet sword.
Make there be one fewer dragon. (Normal difficulty or higher.)
A sharp knife. Find one.
Have fifty potions made.
Learn 8 mage spells at level 3.
Meet the greatest mage in Avernum.
Learn 8 priest spells at level 3.
Return a Crystal Soul.
Dig up 40 caches.
Escape the bonds of gravity.
Fully prove your worth to Avernum.
Avenge the lost Avernites of Cotra.
Sanctify 5 altars.
Slay Elderan.
Find each class of Empire pass.
Discover 70 locations of interest.
Have ten potions made.
Learn a priest spell at level 3.
Return to Avernum from the depths.
Dig up 10 caches.
Survive a long river journey.
Discover 20 locations of interest.
Learn a mage spell at level 3.
Meet an envoy from the deepest caves.
Open a secret door.
Escape the caves above Fort Ganrick.