Here is the full list of all 20 Arkham Horror: Mother's Embrace achievements.
Completed "The Peculiar Monsieur Lanuit"
Completed "Herd of Algedi"
Completed "What Was Lost is Never Found"
Completed "Finding Meaning in the Stars"
Completed "An Invitation"
Completed "Unwelcomed Guests"
Completed "Tendrils of Witchcraft"
Completed "A Morbid Dance in the Second Line"
Save Arkham from the Dark Young
Steal Lanuit's trinket from his store
Visit a Outhouse
Use the same investigator for every scenario of the game
Find the recipe in every scenario
Kill 3 opponents in a single investigator's turn
Use a Radithor on an investigator without any Conditons
Use a Bromo Coffee when you Action points are full
Commit suicide by smoking a cigarette
Heal enemy with a Wild Cast
Kill the Dark Young with a Birthling explosion.
Have 75 items in your Office Chest at one time