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