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.
Slay the commander of the invading army.
Make there be one fewer dragon. (Normal difficulty or higher.)
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.
Dig up 40 caches.
Get a really sweet sword.
Return a Crystal Soul.
Learn 8 mage spells at level 3.
Meet the greatest mage in Avernum.
Fill up a spirit prism.
Escape the bonds of gravity.
Have fifty potions made.
Learn 8 priest spells at level 3.
A sharp knife. Find one.
Fully prove your worth to Avernum.
Find each class of Empire pass.
Slay Elderan.
Avenge the lost Avernites of Cotra.
Sanctify 5 altars.
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.
Meet an envoy from the deepest caves.
Learn a mage spell at level 3.
Open a secret door.
Escape the caves above Fort Ganrick.
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.