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