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