Here is the full list of all 60 The Quest achievements.
Travel 20000 tiles
Mix 100 potions
Perform 500 melee attacks
Cast 250 spells
Kill 100 monsters
Read 12 non-magical books
Find the Sunken Monastery
Complete 10 quests
Get thrown into jail
Mix 25 potions
Drain 1000 health by using spells
Complete Matras infection quest
Cast 50 spells
Kill 25 monsters
Perform 100 melee attacks
Perform 2000 melee attacks
Perform 100 ranged attacks
Perform 500 ranged attacks
Perform 2000 ranged attacks
Cast 1000 spells
Mix 250 potions
Kill 250 monsters
Repair 100 items
Attain 40 base Strength
Attain 40 base Dexterity
Attain 40 base Endurance
Attain 40 base Intelligence
Attain 40 base Personality
Attain maximum positive fame
Attain maximum negative fame
Attain the outfit rank 'Fashionable'
Complete 25 quests
Complete 45 quests
Reach the good ending
Reach the evil ending
Find the treasure island
Find the Abandoned Mine
Break out of jail
Win 100 card games
Complete Nobleman's inheritance quest
Complete Join the Thieves' guild quest
Complete Kill the Witch Queen quest
Pickpocket successfully 50 times
Learn all Undead spells
Learn all Attack Magic spells
Kill the Cyclops King
Amass 100000 gold
Travel with the Sea Captain in every port
Enjoy the services of Madame Rosalia's House of Fleshy Delights
Meet one of the makers of The Quest in game
Kill 10 Firebirds
Complete Bring Eckinish to Dagma quest
Find a use for all Idols on Thule and Eldfell
Kill The Beast
Find the lost spring
Complete Bribe the sea captain Moruu quest
Kill 20 Flesh Eaters
Reach the good ending of Islands of Ice and Fire
Reach the evil ending of Islands of Ice and Fire