Here is the full list of all 20 Druidstone: The Secret of the Menhir Forest achievements.
Complete all missions on Hard without completing any missions with other difficulty levels.
Lock an enemy into a cell.
Defeat the Master Haunt.
Kill 9 enemies with a single action.
Complete a non-tutorial mission without any weapons equipped.
Complete a non-tutorial mission without using any spells.
Complete The Oakshield's Demand under 90 seconds.
Complete all missions with three stars.
Complete a non-tutorial mission without taking any damage.
Kill both Basilisks in The Pyriform Egg.
Complete all missions on any difficulty level.
Complete all main campaign missions.
Complete all puzzle missions.
Collect all Steelface's Crates.
Defeat Mad Eye.
Defeat the Necromancer.
Defeat the Ice Demon.
Gain 20 power gems.
Defeat Oghma.
Collect a thousand gold pieces.