Here is the full list of all 35 Avernum: Escape From the Pit achievements.
Dig up 5 caches.
Enter the Castle at last.
Slay 1000 foes.
The mayor of Formello lost something of great value. Recover it.
Learn a priest spell at level 3.
Get a dread curse. Then cure it.
Learn a mage spell at level 3.
Discover 10 locations of interest.
Purge a nefarious infiltrator from Silvar's sewers.
Open a secret door.
Slay 100 foes.
Escape the tunnels under Fort Avernum.
Learn 6 mage spells at level 3.
Learn 18 mage spells at level 3.
Learn 6 priest spells at level 3.
Learn 18 priest spells at level 3.
Dig up 40 caches.
Have ten potions made.
Have fifty potions made.
Discover 50 locations of interest.
Find the secret at the bottom of Lost Bahssikava.
Sss-Thsss will trouble Avernum no longer.
Steal the treasure from Gremlin's Gold.
Purge a certain powerful demon from the Tower of Magi. Phew. Hope they stay out of trouble in the future.
Find something that lets you fly.
Reform a legendary blade from Avernum's past.
Join the Scimitar.
Meet the Archmage Erika.
Avernum has five dragons. See if you can whittle that down a bit.
Destroy the demon Grah-Hoth, making Avernum safe from his menace at last.
Discover a route back to the surface world. There must be one somewhere.
Deliver harsh vengeance to the cruel tyrant who sent the Avernites into the underworld.
Complete all three game-winning quests in Avernum and never set the difficulty below Normal.
Complete all three game-winning quests in Avernum and never set the difficulty below Hard.
Complete all three game-winning quests in Avernum and never set the difficulty below Torment.