Here is the full list of all 8 The Overdreamer achievements.
Run through under "Mom's" arm when she tries to hit you.
Check all the places in the hospital.
Don't suffer any damage from the roots.
Break all the boxes and glasses at the Boogeyman's place.
Find the orange mushroom.
Check all the pictures in the house and the basement.
Break all the spider eggs before they hatch.
Check all the places in the house.