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.)
Fill up a spirit prism.
Learn 20 priest spells at level 3.
Learn 20 mage spells at level 3.
Keep the Empire from flooding Avernum with troops.
Get a really sweet sword.
Win Avernum a powerful ally in its war.
Dig up 40 caches.
Have fifty potions made.
Learn 8 mage spells at level 3.
Learn 8 priest spells at level 3.
A sharp knife. Find one.
Escape the bonds of gravity.
Meet the greatest mage in Avernum.
Fully prove your worth to Avernum.
Find each class of Empire pass.
Slay Elderan.
Discover 70 locations of interest.
Sanctify 5 altars.
Avenge the lost Avernites of Cotra.
Have ten potions made.
Return a Crystal Soul.
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.