Here is the full list of all 20 AER - there are Memories of Old achievements. It takes around 3-4 hours to unlock all of the achievements on Windows.
Completed the game.
Complete the Monastery.
Find Erin when she's gone.
Complete the Eventide Sanctuary.
Find the Ancient Llamba.
Speak to all of the spirit animals.
Find the bones of an old beast.
Complete the Archives.
Find the statue of the fox.
Find the chiseled stone map.
Find the giant birdshrine.
Discover all areas of the map.
Find the ancient battlefield.
Find the Crab Island.
Step into the well.
Find the statue of the deer.
Get some Lambaby love.
Find the statue of crane.
Find the dwellings of the rift cult.
Escape the collapsing cave.