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