Here is the full list of all 56 Mysterious Realms RPG achievements.
Obtain every other achievement
Complete the game without any Hero dying
Slay the First Warden
Slay Elemental Lord
Slay Goblin King
Slay Grim Reaper
Eat 25 food
Encounter 5 strangers
Empower every Crystal up to 5 power
Reach the maximum of enemy's Health modif.
Complete 20 missions
Slay a hidden enemy
Complete a mission when one Hero is dead
Drink 40 potions
Slay 10 rare enemies
Light 100 torches
Unlock every feature in the Town
Solve 8 riddles
Teach every Hero 6 skills
Encounter 3 strangers
Teach every Hero 4 skills
Eat 10 food
Encounter 25 Events
Drink 15 potions
Examine 15 objects
Complete 10 missions
Slay 100 enemies
Light 50 torches
Open 100 vases, barrels etc.
Pick up 200 gold
Eat 3 food
Solve 3 riddles
Slay 5 rare enemies
Empower every Crystal up to 3 power
Examine 8 objects
Encounter a stranger
Pick up 100 salvage
Encounter 10 Events
Open 50 vases, barrels etc.
Pick up 100 gold
Examine 3 objects
Drink 5 potions
Pick up 40 salvage
Slay 25 enemies
Empower a Crystal up to 3 power
Pick up 30 gold
Open 10 vases, barrels etc.
Slay a rare enemy
Slay 10 enemies
Solve a riddle
Light 5 torches
Teach Hero a skill
Complete a mission
Encounter an Event
Pick up 10 salvage
Slay the first enemy