Here is the full list of all 28 Wizardry: Proving Grounds of the Mad Overlord achievements.
Create a character in the Training Grounds
Create or recruit a character of every class
Change the class of a Level 5+ character in the Training Grounds
Increase all stats of a character to 18
Reach level 5 with a character
Reach level 10 with a character
Reach level 15 with a character
Enter the maze for the first time
Open 100 secret doors
Disarm all trap types
Defeat Murphy’s Ghost on Floor 1
Defeat Monster Allocation Center Encounter on Floor 4
Defeat Werdna and recover the Amulet
Collect all key items in the Maze
Donate 40,000 GP amount of gold to Cant
Stay 52 times at The Adventurers' Inn
Spend 50,000 GP at Boltac’s Trading Post
Recruit 13 Characters
Kill 100 enemies with a single character
Recover 500HP by casting spells
Cast party / character buff spells 25 times
Put a whole group of enemies to sleep
Dispel 50 enemies
Raise a character from the dead
Run from 10 fights
Fully inspect 20 enemies
Fully inspect all enemies
Encounter all enemies