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.
Find Erin when she's gone.
Find the chiseled stone map.
Find the giant birdshrine.
Find the ancient battlefield.
Find the dwellings of the rift cult.
Find the bones of an old beast.
Find the statue of the fox.
Find the statue of crane.
Speak to all of the spirit animals.
Find the Ancient Llamba.
Completed the game.
Complete the Monastery.
Discover all areas of the map.
Complete the Archives.
Complete the Eventide Sanctuary.
Step into the well.
Get some Lambaby love.
Find the Crab Island.
Find the statue of the deer.
Escape the collapsing cave.