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