Here is the full list of all 35 Avernum 2: Crystal Souls achievements.
Slay the commander of the invading army.
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.
Make there be one fewer dragon. (Normal difficulty or higher.)
Learn 20 priest spells at level 3.
Learn 20 mage spells at level 3.
Keep the Empire from flooding Avernum with troops.
Win Avernum a powerful ally in its war.
Have fifty potions made.
Dig up 40 caches.
Get a really sweet sword.
Escape the bonds of gravity.
Fill up a spirit prism.
Return a Crystal Soul.
Meet the greatest mage in Avernum.
Learn 8 mage spells at level 3.
Slay Elderan.
A sharp knife. Find one.
Sanctify 5 altars.
Avenge the lost Avernites of Cotra.
Fully prove your worth to Avernum.
Find each class of Empire pass.
Have ten potions made.
Learn 8 priest spells at level 3.
Discover 70 locations of interest.
Dig up 10 caches.
Learn a priest spell at level 3.
Return to Avernum from the depths.
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.