Here is the full list of all 35 Avernum 2: Crystal Souls achievements.
Open a secret door.
Escape the caves above Fort Ganrick.
Meet an envoy from the deepest caves.
Survive a long river journey.
Return to Avernum from the depths.
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 a mage spell at level 3.
Learn 8 mage spells at level 3.
Learn 20 mage spells at level 3.
Learn a priest spell at level 3.
Learn 8 priest spells at level 3.
Learn 20 priest spells at level 3.
Dig up 10 caches.
Dig up 40 caches.
Have ten potions made.
Have fifty potions made.
Discover 20 locations of interest.
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.