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